Like small-scale Legos clicking into place, nature autonomously puts together microscopic building blocks. Living systems are biochemical machines that excel at building and moving their parts. Just as machines need energy in some form to operate, living systems are energized by consuming “fuel”—substances or food—reliably. The human body, for example, contracts muscles by the motion of tiny nanomotors—molecular devices that convert energy at the nanoscale scale to generate movement at the macroscale. The ability to mimic nature’s self-assembly would revolutionize science’s approach to synthesizing materials that could heal, contract or reconfigure.