Slideshow: Girl to Woman -- Your Changing Body

Puberty usually starts when you're between 9 and 13 years old. But it can start earlier or later. Thanks to hormones like estrogen, you'll notice changes like your breasts starting to grow and new curves forming on your body. You might notice that you start to get taller, and eventually you'll get your period.

You may have noticed hair growing in places you never had it before -- like under your arms, on your legs, and around your pubic area. It usually starts out light and fine, and gets thicker and darker. Body hair is normal, but some girls don't like the way it looks. If you want to get rid of it, ask your mom or a girlfriend how to do it safely.

During puberty, your body will change and continue to grow -- and sometimes the growth happens quickly. This is called a "growth spurt." During this time you can grow as much as 4 inches in a year. Growth spurts usually start between ages 9 and 11. Most girls reach their full adult height by 18. But just like everything else in puberty, you might grow faster or slower than this.

Breasts: You may feel excited about having them or totally embarrassed by them. Either way, wearing a bra or cami may help you feel more comfortable. Ask your mom or a girlfriend to help you pick one out. And if one breast seems smaller than the other, don't worry. This is normal, and the size usually evens out over time. You may also see changes in nipple size and color as your breasts start to grow. That is normal.

It's normal to get pimples -- about 85% to 90% of all kids do. Simple acne may be the first noticeable sign of puberty. You may get acne on your face, upper chest, or back. During puberty, your oil glands go into overdrive, causing acne. Stress, having your period, and oil-based makeup can make pimples worse. Don't pick them. Instead, keep your skin clean and get treatment advice from a doctor. The good news? Acne usually improves by the end of puberty.

If you’ve noticed you're starting to sweat more, you’re not alone. During puberty your 2 million to 4 million sweat glands suddenly become more active. So you might sweat -- especially under your arms -- when you're feeling nervous as well as when you're hot. And you might notice a new smell, too. It's all normal. But if you're worried about smelling bad, try showering every day or using deodorant.

When puberty starts, most girls will begin to notice a vaginal discharge. It's normal to see white or yellow stains in your underpants. This fluid helps keep your vagina clean and moist. But if you ever notice itching, an odor, or discomfort around your vagina, talk to your mom or other caregiver. These could be signs of an infection.

Girls are supposed to have more fat on their bodies than boys. And during puberty you may notice your body has more fat than it did before. At first, it may seem like it's all in your belly. But as you go through puberty, it will turn into curves. Your waist will get smaller and your hips, butt, and thighs will get curvier.

Chances are, you'll get your period around the same age your mother or older sister did. It can happen any time from age 9 to 16. If you're otherwise developing normally, don't worry if you're not on the same schedule as your friends. But while you're waiting, you may want to carry a bag with a few pads or tampons and a change of clothing, just in case. Ask your mom or a friend how to use them. You can experiment with different sizes and styles. 

The extra hormones in your body during puberty may cause problems in your mouth. Your gums may become more sensitive or feel swollen and tender. It's especially important to brush, floss, and see your dentist on a regular basis. Regular care prevents bad breath, gum disease, and other mouth problems.

There's no one "right" age to start dating. It's up to you and your parents to decide when you're ready. You don't have to start dating just because your friends are. Even if you like someone, you may want to get to know the person better before going on a date alone. You can start by talking on the phone or texting. Or you can go out with a group of friends to the movies or the mall.

You may think your legs are too skinny or your stomach is too fat. That's totally normal -- most of us don't like something about our looks. But bodies come in all shapes and sizes. So don't worry if you don't look exactly like the models you see in fashion magazines. Their flaws get erased by professional stylists and airbrushing. Instead, aim for a healthy weight by getting exercise and eating a nutritious diet.

Puberty can be exciting, but it also can be scary. You may have all kinds of feelings as your body changes. And you may have lots of questions. But remember, it's normal and everyone goes through it. So don't be embarrassed to talk about it with your mom, older sister, or your friends. You may be surprised to find out that they have many of the same thoughts and questions as you do.