In genomics, a tool for studying how large numbers of genes interact with each other and how a cell’s regulatory networks control vast batteries of genes simultaneously. A robot is used to precisely apply tiny droplets containing functional DNA to glass slides. Researchers then attach fluorescent labels to DNA from the cell they are studying. The labeled probes are allowed to bind to cdna strands on the slides. The slides are put into a scanning microscope to measure how much of a specific DNA fragment is present.