Amorphous selenium (a-Se) colloid particles have been directly photodeposited onto insulating substrates. Scanning Electron Microscopy (SEM) supported by kinetic adsorption measurements reveals the origin of the photodeposition process. The studies show that film formation occurs through a sequence of particle precipitation, growth, and photoadsorption. A plastic flow and coalescence process creates a continuous monolayer before a fast deposition rate of Se on the deposited materials commences. Surface forces seem to have an important role in the creation of the morphological structures of the adsorbed particles. © 1989, Materials Research Society. All rights reserved.