Boys may be concerned about penis size during puberty. Who is bigger? Who is smaller? Who really cares anyway? Just as each guy is different in height, the size and the shape of the penis varies with each individual male. There is no "right" size. A penis is shorter when flaccid, or soft, and longer during an erection.

An erection occurs when the penis fills with blood, which causes pressure to build up inside it. And, as generations of men will agree, an erection can occur at any time. Any time. It is even normal for guys to get them for no reason at all. It can be kind of embarrassing. Here's some advice for you guys reading this. Just relax and try to focus on something else. When it passes, your muscles relax and it's back to business as usual.

Sometimes an erection happens during sleep. It can actually cause a boy to ejaculate and release semen, the white, sticky substance that carries sperm and shoots out of the body through one opening in the penis. This is commonly called a "wet dream" or a nocturnal emission. Again, it's totally normal.

The scrotum is the soft external sac on a guy's body that contains and protects your two testes, or testicles. Sperm is created in the testicles at the start of puberty and they normally don't stop until death. That's why an 80 year old man can still father a child. It's not common. But it is possible. A single male sperm is also responsible for fertilizing a woman's egg and creating a baby.

Things to remember. All guys face the same changes. These changes won't take place all at the same time, and different guys will go through them at different times. All in all, though, these changes are a healthy sign on the road to manhood.