This work presents the first experimental evidence of the formation of a fractal network of crystalline clusters in the first stage of the amorphous-crystal transformation. Although this transformation has been extensively studied, such an intermediate stage between amorphous and crystalline phases has never been experimentally revealed before. This fractal network was obtained by laser irradiation of an amorphous Te—Se—Br alloy. The irradiation conditions have been determined in order to be in a regime of limited diffusion, which is the basis of fractal formation. Moreover, the fractal dimension has been determined to be 1.55, which corresponds to the theoretical value obtained for fractal growth by a process of cluster-cluster aggregation with some structural readjustment. © 1991, Materials Research Society. All rights reserved.