Penises can be lots of different shapes and sizes. They can be straight or curved, short or long, circumcised or uncircumcised, and all things in between. All of these differences are completely normal and may change through puberty. A penis has lots of different parts to it, but basically there is the top (or ‘the head’) and ‘the shaft’. Inside the penis, there are tubes that link it to the bladder (for peeing) and the testicles (for semen). The testicles or ‘balls’ are found inside the scrotum and are where sperm and semen are produced.  Sperm are tiny cells which can impregnate an egg that is inside the womb – leading to pregnancy. Semen is a whitish liquid that carries sperm and help them travel to reach the egg.  Testicles come in different shapes and sizes and it is common for one to hang lower than the other. Penis and testicle sizes can also change depending on temperature. When aroused, the penis becomes erect to prepare itself for sex. This is sometimes known as a hard on. It is normal to get erections at odd times, such as first thing in the morning, and they can be affected by pressures in your life, such as stress, tiredness and anxiety. Losing an erection at an awkward moment can happen to the best of us, but is completely normal. If you are worried about this, speak to your GP for further support. It’s important to regularly check for lumps and bumps around the genitals. The head of the penis can be sensitive to perfumes and other ingredients found in soaps and shampoos, particularly under the foreskin. We recommend washing with warm water and non-perfumed products to avoid irritation.