As you go through puberty you might find that you sweat more. This is because your sweat glands change and produce more sweat to help control your body's temperature.  It's important to wash regularly and wear clean clothes so that you don't smell but you can also wear deodorant or antiperspirant if you are worried about smelling.

Your periods are a sign that your body is ready to have a baby.  Each month one of your ovaries (you have two) releases an egg. The egg travels down the fallopian tubes and into your womb. The lining of your womb temporarily thickens while this is happening, and if the egg is fertilised by a man's sperm, it will stick in this soft lining and grow.  If the egg is not fertilised, then the lining of the womb breaks down and passes out of your body through your vagina as a small amount of blood, and this is called a period.

You will normally get your period once a month and the average time between the start of one period and the start of another is 28 days. This is called a menstrual cycle.  This is different for everyone, so don't worry if the length of your cycle is shorter or longer than this.

A period lasts a few days and the average length is about five days. Bleeding is usually heaviest on the first couple of days of your period.

The amount of blood you lose during your period is about five to 12 teaspoons full, although it might seem like a lot more.  If you find that you have very heavy periods, you should talk to your doctor as you can take medication to stop this from happening.

Your period will start when your body is ready. Girls usually start their periods around 12 years old, but this is only an average age.  Some girls start their periods much younger and some start when they are older. If you haven't started your period by the time you are 16 years old, you should go to the doctor or nurse for a check-up.

Premenstrual tension or PMT is the name for how some women feel a few days before their period. Around 90 percent of women and girls get PMT and the symptoms can be mild or severe. The symptoms might include:

• Mood swings and irritability
• Unexplained crying/sadness
• Poor concentration
• Tiredness
• Breast tenderness
• Abdominal swelling/bloating
• Cramping in the abdominal area
• Temporary weight gain
• Headache

If you find that PMT is making your life very difficult and you experience any of the symptoms very badly, you should talk to your doctor.  There are some medical conditions that can cause these symptoms to be very bad, and so it’s worth getting check out. You may be able to get some help to deal with them from your doctor.

When you have your period you will need to use something to soak up the blood. There are several different products that you can use and these are the most common:

Sanitary towels or pads are strips of padding which have a sticky side that you can attach to your knickers to keep them in place.  They soak up the blood and keep it contained. There are lots of different sizes of sanitary towels, so you can change them depending on how heavy or light your period is.

Tampons are small cylinders of cotton wool which have a string at one end.  You push these into your vagina and they soak up the blood before it comes out of your body. You use the string to pull it out when you need to change it.  Some tampons have applicators which can make it easier to insert them into your vagina.

Tampons can be hard to get the hang of, so you might want to get used to having your period before you try using them. You shouldn't insert a tampon into your vagina when you are not on your period. If you are not bleeding, a dry tampon can damage you inside and might lead to an infection.

Panty liners are smaller and thinner versions of sanitary towels and are used on days when your period is very light.  You can also use these if you have a lot of discharge in-between your periods.

'Menstrual cups' are small rubber or silicone cups which can be put inside the vagina to catch the blood. The muscles of the vagina keep them in place so they don't fall out. They are then emptied, washed and reused.

Sanitary towels, pads or tampons should be changed every few hours and more if you are bleeding heavily.  Tampons should never be left inside your vagina longer than eight hours.  This can cause something called Toxic Shock Syndrome which is very serious. Some girls prefer to use sanitary towels during the night rather than a tampon.

It's important to keep yourself clean during your period. Make sure you wash regularly and change your sanitary towels or tampons often. This will help stop you getting any infections.

When you first start your periods, you might not be very regular, so you could have a period and then not have another for a few months.  This is normal and not something to worry about. If there is a chance you could be pregnant, you could take a pregnancy test or speak to your doctor or family planning adviser about it. Even if you don't think you are pregnant, if you haven't had a period for quite a while and are worried, you can always talk to your doctor about it and have a check up. 

You can start wearing a bra whenever you want to.  If you feel that you would be more comfortable wearing one, then it's the right time for you. It's important to get fitted for a bra in a department store or specialist bra shop so that you make sure you are wearing the right size.

Breasts come in all shapes and sizes and they are all normal! Bodies grow at different rates during puberty so although it's hard, try not to compare yourself with anyone else. The size and shape of your breasts will continue to change throughout your life.  Lots of things can affect their size and shape like losing or gaining weight, pregnancy and breastfeeding.

It's normal to have sexual thoughts and feelings, especially during puberty when your body is changing. It can be confusing and strange at first but it isn't unusual. Your feelings should calm down after while when your body adjusts to the changes. Read more on our sex advice page.

Masturbation is when you touch your body and your genitals and make yourself orgasm or come.  Both girls and boys masturbate and it's completely normal. It's a way of discovering your body and how it makes you feel and what kind of things make you feel good. Some people might say that it's wrong or that you shouldn't masturbate, but it's a normal part of life and not something to be ashamed of.