Using cutting-edge time-lapse photography, Keck School of Medicine researchers have discovered clues to the development of the head at the cellular level, which could point scientists to a better understanding of how organs and birth defects form in humans. A team of researchers at the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC has for the first time determined the role of two important molecular signaling pathways that help control the number and position of repeated units of cells that pattern the head and face.