Proper functioning of a healthy brain depends on precisely coordinated actions of the different cell-types; neuron, glia and others, that comprise the adult brain. The specified roles played by each of these cell-types are governed by carefully orchestrated genetic programs that control both the ‘dynamic’ as well as the ‘housekeeping’ properties of these cells. We investigated neural stem cells and mature neurons in the adult brain, to gain insights into the genetic programs that underlie the proper fate and functions of these cells throughout a lifespan. In this talk, I will present our recent findings; two studies, one that unveil a ‘dark-side’ of the adult neural stem cell, and another that provides clues for novel gene-networks underlying adult neuronal maintenance. I will place these findings in the context of adult brain homeostasis, and discuss how elucidation of homeostatic regulations can help gain better insights into pathological conditions.