What do cancer and the growing legs of a fruit fly have in common? They can both be influenced by a single molecule, a protein that tends to call the shots. Present in virtually every creature on the planet, this protein goes by the name Epidermal Growth Factor Receptor protein, or EGFR. Now a team of neuroscientists has figured out how to tease apart the many roles EGFR plays in the body — challenging conventional wisdom in the process.