Immature muscle cells fuse during development to form long muscle fibers with many nuclei. To identify the factors involved in the fusion process, the scientists studied fibroblast cells that do not fuse normally. As shown in the microscopic image, adding a gene that makes a protein called myomerger to fibroblasts causes them to fuse into clusters of fluorescently stained cell nuclei. The protein works in tandem with another protein, called myomaker, to cause fusion. By gaining a better understanding of the processes involved in muscle development and regeneration, research could contribute to the development of new therapies for muscle disorders.