While most of the research in our lab is directed at understanding the function of nucleic acids as they are found in nature, the spider project focuses on studying artificial devices constructed from nucleic acids. Our collaborators developed a tiny molecular robot called a “spider” possessing four “legs” made of single-stranded DNA. About a million times smaller than its namesake, the molecular spider uses its legs to bind to specific nucleic acid strands on a surface. The legs are designed to cleave, or cut, the strands that they are bound to in the presence of certain metal ions. Because its legs bind more weakly to strands that have been cleaved, the spider is designed to avoid sites it has already visited and progress to new regions on the surface. Using single-molecule fluorescence techniques, we track the movement of these spiders and determine ways of best characterizing the walking behavior. In the future, such nanometer-sized robots could be used to carry out complex tasks at the molecular scale.