Proteins are the doers of biology. In the human body, they perform most of the work in cells and are required for the structure, function and regulation of the body’s tissues and organs. Each protein is made of a precise sequence of amino acids that allows it to fold up into a three-dimensional shape determining its function. In the past, the all-important structure of a protein could only be captured by difficult and time-consuming laboratory analysis. Now comes a dramatic new turn—a window on life’s basic building blocks.