Coplanar nanostructures consisting of two different types of organosilane monolayers have been fabricated using scanning probe microscopes (SPMs) and served as templates for the area-selective immobilization of various materials. The first organosilane monolayer; which had been uniformly prepared on a substrate, was locally degraded through electrochemistry of adsorbed water at the junction of the monolayer and the SPM probe. This probe-scanned region chemisorbed molecules of the second organosilane, resulting in the creation of a self-assembled monolayer (SAM) confined to the SPM-defined pattern. Latex nanoparticles or proteins selectively assembled onto this patterned SAM.