An accurate communication between motor neurons and skeletal muscle fibers is required for the proper assembly, growth and maintenance of neuro muscular junctions (NMJs). Several signaling and extra cellular matrix molecules play stimulatory and inhibitory role son the assembly of functional synapses. Studies in Drosophila have revealed crucial functions for early morphogens, such as members of the Wnt and Bone Morphogenetic Proteins (BMP) signaling pathways, during the assembly and maturation of the NMJ. Here, we bring to gether recent findings that led us to propose that BMPs also work in vertebrate organisms as diffusible cues to communicate motor neurons and skeletal muscles.