The ribo-viroxic-nucleic structure of humanoid DNA controls certain chemical and genetic changes in humanoids as they reach puberty. Unlike most of the humanoid DNA strand, the ribo-viroxic-nucleic structure actually changes at puberty, beginning the next phase of aging.
In 2368, due to interference from a molecular reversion field, Captain Jean-Luc Picard, Keiko O'Brien, Ensign Ro Laren, and Guinan had their ribo-viroxic-nucleic structures removed from their DNA during transport. They re-materialized as children, though all their memories and mental capacities remained those of adults. They were subsequently returned to their correct physical appearances when they were transported again and the structures were restored. (TNG: "Rascals")