This graphic shows a molecular robot (automaton) in action. To tag cells (grey circle) that display the Mi, Mj, and Mk receptors, five different components of a molecular robot are deployed. Each of the first three components consists of DNA and an antibody; one antibody binds to each receptor, bringing its DNA (represented by the colored lines) close together on the cell. The fourth DNA component, represented by the single red line, then initiates a chain reaction by pulling the red DNA strand away from the first antibody. That causes the blue DNA strand to change position, followed by the green DNA strand. In the final step, the last antibody pulls a fluorescent DNA strand (labeled F) from the fifth component, completing the action of the robot.