Humans possess different types of muscles. While the heart pumps blood through our vessels, skeletal muscles allow us to lift weights or run marathons. Depending on their specific function, the different muscle types adapt their molecular architecture. Particular combinations of protein subunits form variants of the contractile apparatus of the muscle, the sarcomere. Studying the flight muscles of the fruit fly Drosophila, scientists at the Max Planck Institute of Biochemistry in Martinsried near Munich, Germany, discovered an important concept explaining how the contractile machinery of the flight muscles is built differently to other body muscles. The results published in the journal EMBO Reports may help to eventually understand and treat human myopathies or cardiomyopathies.