Inside the fertilized egg cell of a fruit fly, we see a type of myosin, related to the protein that helps our muscles contract, made to glow by attaching a fluorescent protein. At the start of the movie, the myosin proteins are distributed relatively evenly near the surface of the embryo. The proteins temporarily vanish each time the cell's nuclei--at this point buried deep in the cytoplasm--divide. When the multiplying nuclei move to the surface, they shift the myosin, producing darkened holes. The glowing myosin proteins then gather, contract, and start separating the nuclei into their own compartments. Courtesy of Victoria Foe, research professor at the Center for Cell Dynamics, University of Washington's Friday Harbor Laboratories.