Abstract: A cryo-cell assembly for biological material including a space for receiving the material, the space being at least partly enclosed by means suitable for conducting heat from the space to a heat sink and including heat generating means in heat conducting relationship with the space. Power is applied to the heat generating means according to a desired temperature cycle stored in memory. The power supply unit senses actual temperature in said space and compares this with the desired temperature. Power is supplied to the heat generating means whenever the actual temperature falls below the desired temperature.