The modelling of three-dimensional structure of materials and the computer processing of micro-structure are applied, where the structure of materials is investigated by microscope. It is a relatively new interdisciplinary scientific field, the significance of which has gradually been increasing since the beginning of 1980's and today it has become one of the key field of researches of material structure. The present paper gives a short review about the theory of stereology, which is well founded mathematically. The relatively new fractal models are described from the micro-structural models having a great significance from the point of view of materials science. The image transformations, the development of binary images and the binary procedures are illustrated by showing the practical tasks of materials science. The microstructure of metal matrix composites reinforced by carbon fibres, the possibilities of characterising the dendritic structure developing during the solidification of transparent materials, the characterisations of ceramic grains in the Al-base composite are shown.