Highly regenerative tissues such as blood, skin, gut and testis are maintained by rare populations of tissue specific stem cells. Throughout the life of the organism stem cells replace cells spent to normal turnover and repair. Unlike their embryonic counterparts, tissue stem cells are already committed to their lineage and must achieve a perfect balance with differentiated progeny. A major control-unit that regulates this balance is the stem cell microenvironment, known as the niche. In our lab we focus on stem cell – niche communication and on mechanisms that maintain such unique cell compartments. We are mainly interested in post-transcriptional mechanisms as regulation at the mRNA levels enables the dynamics required for continuous stem cell activity. The highly regenerative Drosophila testis and S2 culture cells are the main research systems in our lab.