sentence: Scientists call making sperm 'spermatogenesis'.
sentences_before: As well as being chemical-producing glands, testicles are gonads. Apart from 'hormones', the other important substances made by the testicles are spermatozoa, which are generally just called sperm.
sentences_after: Boys begin making sperm when they start growing into men, at a time of life called puberty.
concept_name: scientist
headings: Testicle Function Making sperm
categories: Anatomy of the male reproductive system Glands