Menstruation is the result of your body’s monthly opportunity to create a baby. When your body first becomes able to produce a child, usually between the ages of 9 and 16, it begins preparation once a month for possible motherhood. Your ovaries release an egg, which travels to your uterus and waits to be fertilized by a man's sperm. If the egg is fertilized, you become pregnant, and your body begins making changes to grow a child. But when you’re not pregnant, the uterus sheds its lining and flushes it out, along with some blood and body fluids. For two to six days each month, this stuff flows out of your body through your vagina as reddish-brown menstrual flow.

It’s hard to predict exactly when you’ll get your first period, but a good guess is about two years after you start going through puberty. At the beginning of puberty, you'll notice that your breasts are developing, you’re getting taller, and you're starting to grow a little hair under your arms and on your genitals (pubic hair). A good sign you're getting close is a thick, white mucous discharge coming from your vagina. Usually, this happens about 6 months before you get your first period.

No. Heredity, hormonal birth control, and overall health can all determine how much you bleed. Your first period might be very light and could show up in your underwear as a brownish, sticky stain or a few drops of red blood. During the course of your period, you’ll lose about four tablespoons of fluid. For reference, the average human body contains about 10 pints of blood, or 320 tablespoons, so during your period, you only lose about 1 percent of the blood in your body. Your flow won’t necessarily be the same all the time, but even girls who bleed heavily only lose up to 8 tablespoons of blood during their periods. Your flow can also change throughout the day depending on how active or still you are that day.

The color of your menstrual blood can be various shades of pink and red, to brown and near black. You could experience all these colors during a period or just one. The color of your period is influenced by how fast or slow your menstrual blood is flowing. Faster flow tends to be bright red, while slower flow may have a dark brown, near black hue. You also might notice that the texture of your period varies. It can be thin, like blood from a cut, or thicker with clots.

Only if you tell them. You don’t look different when you’re on your period, and period blood doesn’t have an odor, so there’s no way for anyone to tell. Some girls don't mind telling their friends and family members when they’re on their period, but plenty of others choose to keep this information private. Whether you choose to use a pad or a tampon, no one will see it underneath your clothing. While you may not want to tell the world you’re on your period, remember – it's nothing to be ashamed of.

Each girl is different – you’ll know when something is wrong if it seems unusual for your body. For example, if you start needing to change your pad a lot more often, or if your cramps seem worse than they were before, you may want to talk to someone about it. If you have heavier bleeding than usual; vaginal itching, burning, or other pain; severe cramps that don’t go away; extreme mood swings or depression; or sleep disturbances, you may want to talk to a healthcare professional.

You could get pregnant even before you have your first period. Pregnancy requires a fertilized egg, and ovulation occurs before your period, so a girl could be ovulating before her first period happens. Periods signal that a girl’s body is physically ready to begin reproduction, even though she may not be emotionally ready to have sex yet. If you are sexually active, use birth control even if you haven’t gotten your first period – there’s no guarantee you won’t become pregnant.

For the first few years you get your period, it may not come regularly while your body continues to grow and mature. Most cycles will become consistent within two years of starting menstruation. But even after your periods have evened out, there are lots of reasons you could miss one, including strenuous exercise, stress, pregnancy, illness – or it could just be a fluke. Some girls find their periods come early or are delayed a few days when they’re really active in sports, or during a stressful time, like finals week. If you think you could be pregnant, or you miss more than three periods at a time, see your healthcare professional.

Everyone’s vagina has a unique smell, just like skin or sweat. Most of the time, if you bathe regularly, no one else can smell your personal scent. And your scent can change over time and with your cycle. As your body is ramping up to ovulate, you will have clear, thin vaginal discharge with little or no odor. If there is an odor at all, it is slightly sweet smelling due to the acidity of the vagina. After you ovulate, your mucus gets thicker and slightly whitish in color and will smell a little like vinegar. Avoid using douches or perfumed body washes in your vagina, as these can cause infection and make odor worse. If you suddenly smell more strongly than normal, or if you smell a foul odor, you may have an infection and should see a healthcare professional.

Vulvas come in all shapes, sizes, and colors, and no two are exactly alike – there’s no particular way you’re “supposed” to look. Every vulva has a clitoris, labia majora and minora, and urethral opening, but they can look completely different from girl to girl. Sometimes the inner lips are wrinkly and hang out a little even when the outer lips are closed, and other times, the inner lips stay inside and all you see are the outer lips. Some girls trim their pubic hair for personal or religious reasons, while other girls let it grow naturally. If you want to, you can use a mirror to help you see what your vulva looks like.