Abstract: The decomposition of cells of biomasses or the like or of substrates containing biomass, e.g. for releasing cell content substances, for separating cell content and cell sheath or for inactivating enzymes or the like is performed by heating and expanding. According to the invention, the biomass or the like is heated by friction, optionally under pressure, to temperatures above the point of evaporation of water and it is subsequently expanded into atmosphere or in a reduced pressure. As for the apparatus, the cells of biomasses or the like are decomposed by means of a centrifugal machine in which a rotor and a stator with facing radial surfaces are coacting. Between the rotor and the stator, there is provided a gap producing frictional heat in a predetermined amount for the material passed continuously therethrough, and at the outlet of the gap, there is an expansion chamber which is in communication the atmosphere.