Did you ever wonder what all those complex body systems do? Use this medical library to find out about basic human anatomy, how it all functions, and what happens when things go wrong.

Find out about the mysterious, life-sustaining fluid called blood.

Our bones, muscles, and joints form our musculoskeletal system and enable us to do everyday physical activities.

If the brain is a central computer that controls all the functions of the body, then the nervous system is like a network that relays messages back and forth to different parts of the body. Find out how they work in this Body Basics article.

Most people think digestion begins when you first put food in your mouth. But the digestive process actually starts even before the food hits your taste buds.

Hearing is their main job, but it's not all your ears do. Find out all about them in this body basics article for teens.

The endocrine system influences almost every cell, organ, and function of our bodies. It is instrumental in regulating mood, growth and development, metabolism, and sexual function, among other things.

Although your eyes are small, their structure is incredibly complex. Find out how they work in this body basics article.

Why do girls get periods? What goes on when a woman gets pregnant? What can go wrong with the female reproductive system? Find the answers to these questions and more in this article for teens.

The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues.

See how the joints work.

The immune system is made up of special cells, proteins, tissues, and organs that defend people against germs and microorganisms.

The kidneys perform several functions that are essential to health, the most important of which are to filter blood and produce urine.

Each day you breathe about 20,000 times. Find out more about the lungs and breathing process.

What makes up a guy's reproductive system and how does it develop? Find the answers to these questions and more.

Your body gets the energy it needs from food through a process called metabolism. Get all the facts on metabolism in this article.

Did you know that your mouth is the first step in the body's digestive process? Or that the mouth and teeth are essential for speech? Learn about the many roles your mouth and teeth play.

Our skin protects the network of tissues, muscles, bones, nerves, blood vessels, and everything else inside our bodies. Hair and nails are actually modified types of skin.

The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections.

Insomnia can be a big problem for teens. Read our tips on getting a good night's sleep.

Backpacks help you to stay organized. They're also better for carrying school supplies than messenger or other shoulder bags. But can they cause health problems?

Sleep problems can keep some teens awake at night even when they want to sleep. If that sounds like you, find out what you can do.

Most small cuts, scrapes, or abrasions heal on their own. Here are tips for teens on how to treat cuts at home - and when to get medical help.

Earbuds are basically a tiny pair of speakers that go inside the ears. They're fine at low volumes, but they can cause permanent hearing loss if not used properly. Find out what's safe (and not) in this article for teens.

Finding it hard to fit in fitness? Try these simple exercises for teens.

Teens need about 8 to 10 hours of sleep each night. But you might not be getting it. Here's why - and tips for getting more shut-eye.

The testicular self-examination (TSE) is an easy way for guys to check their own testicles to make sure there aren't any unusual lumps or bumps - which are usually the first sign of testicular cancer.

Puberty causes all kinds of changes in your body - and some may not make you feel very desirable. Read this article for information on dealing with greasy hair, perspiration, and body hair.

A toenail is ingrown when it begins to break through and grow into the soft skin of the toe. Find out more about ingrown toenails.

Experts now know that breathing in someone else's secondhand smoke is bad for you. Find out what you can do about it.

If you have sickle cell trait, find out the best way to keep yourself healthy.

Here are some practical, everyday tips on making exercise and healthy eating work for you instead of feeling like it's the other way around.

There's a lot more to taking care of your teeth than breath mints and mouth sprays. Read this article to learn the facts on flossing, how to give plaque the brush-off, and much more.

Even if you're lucky enough to have perfect vision, taking care of and protecting your eyes is vital to keeping your peepers perfect. Learn all about how to take care of your baby blues (or browns or greens) in this article.

When it comes to pads and tampons, there are lots of choices. It may take some experimenting before you find what works best for you. Here are some tips.

Sending and receiving messages late at night can disrupt your sleep and leave you tired and unfocused when it's time for school.

Sometimes it may seem like your skin is impossible to manage, especially when you find a huge zit on your nose or a cold sore at the corner of your mouth. Here are ways to prevent and treat common skin problems.

Bad breath, or halitosis, can be a major problem, especially when you're about to snuggle with your sweetie or whisper a joke to your friend. The good news is that bad breath often can be easily prevented.

Getting the right amount of exercise can rev up your energy levels and even help you to feel better emotionally. Find out why.

If you're afraid of shots, you're not alone. Next time your doc asks you to roll up your sleeve, try these tips.

Get tips for fending off the flu in this article for teens.

Stay well and have a good time over the holidays - even if everyone else is falling apart. Our 5 tips will help boost your body's defenses.

Blood might look the same and do the same job, but tiny cell markers mean one person's body can reject another person's blood. Find out how blood types work in this article for teens.

There's a 97% chance that someone you know will need a blood transfusion. Blood donors — especially donors with certain blood types — are always in demand. Find out what's involved in this article for teens.

News reports on health and medicine can be confusing —and sometimes downright scary. How do you know what is important and accurate?

Genes play an important role in how we look and act, and even in whether we get sick. This article gives the lowdown on genes, genetic disorders, and new research into gene therapy.

Germs are tiny organisms that can cause disease - and they're so small that they can creep into your system without you noticing. Find out how to protect yourself.

Medicines can cause problems if they get into the water supply or the wrong hands. Find out how to dispose of old or unused meds safely in this article for teens.

Did you know that the most important thing you can do to keep from getting sick is to wash your hands? If you don't wash your hands frequently, you can pick up germs from other sources and then infect yourself.

Taking charge of your own health care is a big step, and it can be a little overwhelming. Here's a quick crash course on insurance for teens.

Health insurance has a language all its own. This article for teens explains what some key terms mean.

Taking responsibility for your own health care means understanding things like prescriptions. Read our tips for teens on filling a prescription.

Tips and advice for teens on refilling a prescription.

Missing out on shots puts you at more serious risk than you might think. That one little "ouch" moment protects you from some major health problems.

Find out what the experts have to say.

Each time you hop up on a doctor's exam table, somebody makes a note in your medical records. There may come a time when you need your medical information, so find out how to get it and how it's protected.

If you're afraid of shots, you're not alone. Next time your doc asks you to roll up your sleeve, try these tips.

Medicine doesn’t cure ADHD. But it does help boost a person's ability to pay attention, slow down, and have more self-control. This article for teens has details on how ADHD medicines help.

Adolescent medicine doctors are specialists who have extra training in the medical and emotional issues that many teens face.

Just getting braces and have no idea what to expect? Had braces for a while but wonder what's going on in there? Whatever your situation is, you're not alone: millions of teens have braces.

Doctors use several different types of allergy tests, depending on what a person may be allergic to. Find out what to expect from allergy tests.

Here's a basic look at what anesthesia does.

Here's a quick look at what may happen before, during, and after you get anesthesia.

A basic metabolic panel (BMP) is a group of blood tests that provide doctors with clues about how the body is working. Find out why doctors do this and what's involved for teens.

This common blood test helps doctors gather information about a person's blood cells and how they're working. Find out why doctors do this test and what's involved.

This group of blood tests provides doctors with clues about how the body is working. Find out why doctors do these tests and what's involved for teens.

If your liver isn't working properly, it can affect your overall health. Find out why doctors do liver function tests and what's involved for teens.

Millions of people a year get blood transfusions in the United States. This article explains why people need them and who donates the blood used.

Blood might look the same and do the same job, but tiny cell markers mean one person's body can reject another person's blood. Find out how blood types work in this article for teens.

It's rare for teen girls to have breast problems. But sometimes a doctor or nurse might think a breast exam is a good idea. Find out why, as well as what's involved in a breast exam.

Breast reduction surgery is a procedure that makes large breasts smaller. It can help when large breasts create problems.

Chemotherapy (chemo) is treatment with medicines that stop the growth of cancer cells. Find out how chemo works and what to expect when getting treatment.

You deserve medical care from someone who helps you feel comfortable and understood. Get tips on finding the best doctor for you.

Because EHRs improve how well your doctors talk to each other and coordinate your treatment, they can enhance your medical care. Get the facts on electronic health records.

Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful. Here's how they're done.

Medicines can cause problems if they get into the water supply or the wrong hands. Find out how to dispose of old or unused meds safely in this article for teens.

Girls should get their first gynecological checkup between ages 13 and 15. Find out what happens during a yearly gyn visit -- and why most girls don't get internal exams.

Whether you feel confused, worried, scared, or excited, you'll want to know how your life will change, what you can do to have a healthy baby.

Taking charge of your own health care is a big step, and it can be a little overwhelming. Here's a quick crash course on insurance for teens.

Health insurance has a language all its own. This article for teens explains what some key terms mean.

If you have a mental health problem or you just need support through a tough time, it can help to talk with someone. Here's how teens can find that help.

Need to get a blood test? An MRI? These videos show what happens in 10 of the most common medical tests.

A Pap smear is a medical test that helps doctors figure out if there are any problems with a girl's cervix. Find out what happens during a Pap smear.

A pelvic exam is where a doctor or nurse practitioner looks at a girl's reproductive organs (both outside and internally) and feels the uterus and ovaries to be sure everything's normal. Find out what's involved in this article for teens.

Physical therapy helps people get back to full strength and movement - and manage pain - in key parts of the body after an illness or injury.

Lots of images may come to mind when you think of plastic surgery. This special type of surgery involves a person's appearance and ability to function.

You're probably used to answering your doctor's questions, not asking your own. But it's your body, and you can ask about anything you want. Here are ideas to help you get started.

Find ways to feel good and live a healthy life with sickle cell disease.

If you have sickle cell trait, find out the best way to keep yourself healthy.

Figuring out health care is part of becoming an independent adult. Here are tips for teens on what that involves, and how to choose your own doctor.

People who play a role in their own health care make better decisions and stay healthier. Here are tips for teens on how (and why) to build a bond with your doctor.

You may be wondering why the doctor needs to do a testicular exam. Find out in this article.

Doctors recommend that all teens get vaccinated against the flu. Here are the facts on flu vaccines.

Medicines can cure, stop, or prevent disease; ease symptoms; or help in the diagnosis of illnesses. This article describes different types of medications and offers tips on taking them.

You probably can't wait to get back to your normal activities, but it takes a while for a limb that's been in a cast to finish healing. Here's what to expect.

Knowing what to expect with surgery before you get to the hospital can make you less anxious about your surgical experience - and less stress helps a person recover faster.

Scheduled for a hospital stay? Knowing what to expect can make it a little easier.

Doctors can treat medical problems and sometimes cure them. But what's the difference between a "treatment" and a "cure"? Find out.

Find out what the experts have to say.

How well a wound heals depends on where it is on the body and what caused it – as well as how well someone cares for the wound at home. Find out what to do in this article for teens.

Acanthosis nigricans is a darkening and thickening of the skin that can be a sign of other medical conditions. Find out more.

Almost every teen gets acne at some point. This article addresses common questions and concerns about acne and tells you what you can do about it.

Blisters, calluses, and corns can be uncomfortable, but they're also pretty common and easy to prevent. Find out what to do in this article for teens.

Wondering whether you should pierce one of your precious parts? Read about what to expect.

Learn about bruises, why they happen, how to make them go away faster, and why they turn all those funny colors.

Scars from acne can seem like double punishment - first you had to suffer through the pimples, now you have marks to remind you. Is there anything you can do?

Cellulite is the lumpy look ("cottage cheese") commonly found on the thighs, stomach, and butt. It's due to collections of fat that push against the connective tissue beneath the skin.

Cold sores (also known as fever blisters) are pretty common and lots of people get them. So what causes them and what can you do?

Most small cuts, scrapes, or abrasions heal on their own. Here are tips for teens on how to treat cuts at home - and when to get medical help.

If you're worried about dandruff, you're not alone. Dandruff can start in puberty, and lots of teens and adults live with it. Learn how to control it.

Eczema is a common skin problem. Find out more about it and how you can deal with the skin stress.

You can buy dozens of products for getting rid of unwanted hair. How do they work? And how do you use them?

Did you know that the most important thing you can do to keep from getting sick is to wash your hands? If you don't wash your hands frequently, you can pick up germs from other sources and then infect yourself.

Lice aren't dangerous, but they do spread from person to person easily. They can also be hard to get rid of. Find out how to prevent lice -- and what to do if someone you know has them.

Hives cause raised red bumps or welts on the skin. They're pretty common and usually not serious. Find out what to do about hives in this article for teens.

Find out what the experts have to say.

Tanning beds are no safer than the sun -- and may be even more dangerous. Read this article to get the details, and to find out what is safe when it comes to getting that golden glow.

A toenail is ingrown when it begins to break through and grow into the soft skin of the toe. Find out more about ingrown toenails.

Melanoma is different from other skin cancers because it can spread if it's not caught early. Find out how to lower your risk of getting melanoma and how doctors treat it.

The skin rash molluscum contagiosum isn't a big deal. Find out what to do about it in this article for teens.

Follow these shaving tips for guys and get a quick, easy, and painless shave.

Your skin is usually fairly elastic, but when you grow or gain weight really quickly (like during puberty), you may get fine lines on your body called stretch marks.

The sun can do a lot more than just give you a warm summer glow. Get the facts on sun and skin damage - and what you can do to protect yourself and still look tan.

What's the safest way to get a tattoo? Does it hurt? What can go wrong? Knowing the facts will help you decide whether a tattoo is a good idea for you.

Sometimes it may seem like your skin is impossible to manage, especially when you find a huge zit on your nose or a cold sore at the corner of your mouth. Here are ways to prevent and treat common skin problems.

Vitiligo is a loss of skin pigment that causes white spots or patches to appear on the skin. It's not medically dangerous, but it can affect a person's appearance. Find out more.

Most warts are easy to treat and are rarely cause for alarm. Read this article for more information on warts and how to get rid of them.

There's no sure way to prevent acne. But these tips might help reduce the number and severity of your breakouts.