A morphogen is a signaling molecule that plays a crucial role in the development of organisms. It helps to determine the fate of cells by providing positional information during embryonic development. Morphogens are distributed in a gradient, meaning their concentration varies in different areas, guiding cells to differentiate into specific types based on their location. One well-known example of a morphogen is Sonic Hedgehog, which is essential for the proper formation of limbs and the central nervous system in vertebrates. Morphogens interact with receptors on cell surfaces, triggering a cascade of events that lead to changes in gene expression and cell behavior.