Work from IMBB has uncovered a role for bHLH-O (a.k.a. Hes) proteins Dpn and E(spl) in neural stem cell maintenance in Drosophila. By exerting an anti-differentiation activity they ensure long-term proliferation, which is needed to produce the myriad of neural cells. However, aberrant cell signalling that leads to bHLH-O overexpression can cause pathological over-proliferation of neural stem cells. Zacharioudaki et al, Development 2012.