Puberty is an important step in human development. Onset of puberty, including neurobiological mechanisms important for the increase of hypothalamic GnRH pulses remains a mystery. After birth, GnRH secretion remains elevated and then decreases during childhood regardless of any steroid gonadal feedback. This period of quiescence of the gonadotropic axis during childhood is linked to a central inhibition of GnRH secretion which is replaced by an activator tone at puberty. The study of the pathology of the pubertal timing, including delayed puberty led to the discovery of new genes involved in the migration of GnRH neurons and genes involved in the neuroendocrine regulation of the gonadotropic axis. Recently, the emphasis on the importance of the kiss/GPR54 system in modulating control of the gonadotropic axis at puberty has recently emerged from Human genetics studies.