Transmission electron microscopy is the most natural tool for investigating in detail the physical and metallurgical changes produced in optical storage media by laser writing. Examples of laser writing in bilayer media with low melting points such as Te/Se and Te/C are compared with laser-written spots in metal silicide bilayers formed by the deposition of amorphous silicon onto tellurium, rhodium or gold. Particulate gold films with and without carbon coatings are investigated as potential storage media. Simulated life tests performed by annealing are presented for some of the media. © 1983.