Dip-Pen Nanolithography is a form of scanning probe lithography that uses an atomic force microscope (AFM) tip to "write" with molecules. The AFM tip is dipped into a chemical solution, and then it "writes" patterns on a substrate by delivering the molecules to specific locations. This technique allows for the creation of extremely precise and complex nanostructures, which can be used in a variety of applications, including the development of nanoelectronics and biosensors.