Program aims to identify molecules that contribute to a variety of health benefits. It is well-known that exercise is good for you, but how exactly does physical activity improve the function of different tissues and organs in the body? What molecules underlie how physical activity is translated into better health? The National Institutes of Health’s Common Fund launched a program that aims to catalogue extensively the biological molecules that are affected by physical activity in people, identify some of the key molecules that underlie the systemic effects of physical activity, and characterize the functions of these key molecules.