Researchers from North Carolina State University have found that diffusion plays an unexpected role in cell differentiation during the early stages of development in the embryos of Drosophila, or fruit flies. Instead of spreading a molecular signal out, it was found that diffusion, facilitated through a carrier molecule, actually concentrates the signal in one place. This “facilitated diffusion” mechanism has previously been found in other systems, and the new finding indicates it may be more widespread than previously thought.