Shell-dwelling cichlids take intense care of their offspring, which they raise in abandoned snail shells. A team at the Max Planck Institute for Biological Intelligence used 3D-printed snail shells to find out what happens inside. The young and the mother each follow their own, but synchronized schedules: as soon as the larvae prefer light, they leave the shell on the ninth day after fertilization. The mother, in turn, follows a strict brood-care routine to prevent the young from emerging before this day. The study thus identifies important innate processes during the brood care of cichlids and highlights the complex interplay of different behaviors.