The testis is the primary reproductive organ present in the male.
It contains follicular cells which undergo meiosis to form sperms. Sperms are the male gametes which fuse with an ovum to form a zygote. Zygote later develops into the foetus and then to a newborn baby.
Its interstitial cells secretes testosterone hormone which promotes the growth and development of secondary sexual organs like the penis and secondary sexual character like the growth of body hair, muscle, deepening of the voice.