In the March edition of biobytes Craig Morrell (John Hopkins University School of Medicine, Baltimore) tells us about a brain factor that also promotes blood-clotting, we find out from Dennis Discher (University of Pennsylvania, Philadelphia) how macrophages stop short of swallowing 'self' cells, Norma Andrews (Yale University, New Haven) explains how membranes are repaired by endocytosis and exocytosis, and we learn about a downside of an innate antibacterial response. Written, presented, and produced by Ruth Williams.