Thermochemical nanolithography (TCNL) or thermochemical scanning probe lithography (tc-SPL) is a scanning probe microscopy-based nanolithography technique which triggers thermally activated chemical reactions to change the chemical functionality or the phase of surfaces. Chemical changes can be written very quickly through rapid probe scanning, since no mass is transferred from the tip to the surface, and writing speed is limited only by the heat transfer rate. TCNL was invented in 2007 by a group at the Georgia Institute of Technology. Riedo and collaborators demonstrated that TCNL can produce local chemical changes with feature sizes down to 12 nm at scan speeds up to 1 mm/s.