Dear kacha_42,

Guys start producing spermatozoa (or sperm, for short) at the onset of puberty. Puberty starts at different times for different people. Boys usually start puberty when they're around 10 or 12 years old, though some start a little sooner and others a little later. There’s a cool word for when a guy first produces sperm — spermarche (SPERM-are-key).