How do I explain the concept of puberty to my 12-year-old son?

Puberty has natural, apparent signs, some of which are common to both males and females, and some are specific to females.

As for the common signs, they are:

1. Nocturnal emission (ihtilam): The discharge of semen while awake or asleep.

2. Hair growth (inbat): The appearance of pubic hair that requires shaving.

3. Reaching the age of fifteen lunar years.

As for the signs specific to females, there are two:

1. Menstruation (hayd).

2. Pregnancy (haml).

So, if any of these signs appear on the son, he is considered an adult (baligh).