Susan Lindquist describes protein folding, and how this phenomenon allows orgnisms to evolve rapidly in response to new environmental conditions. All proteins start out as long strings of amino acids. Before a protein can function, it must fold into an extremely precise, highly complex structure. This is a difficult feat in the highly concentrated environment of the cell. Protein folding is facilitated by helper proteins called molecular chaperones. Lindquist's recent work suggests that the forces that govern protein folding exert a profound effect in determining how the genes encoded by an organism's DNA are translated into phenotypic traits. The folding mechanisms of molecular chaperone proteins can allow organisms to reveal accumulated-but-hidden genetic variation in times of stress.