An apparatus for producing crystals of a macromolecule in microgravity includes a container 100 which is made of a material having a low thermal conductivity and an open end. A thermally conductive lid 102 is fitted on the open end of the container to close the container and a heat source/sink 114 is provided in thermal contact with the thermally conductive lid to generate a temperature gradient within the container. When a solution of the macromolecule is provided in the container, the temperature gradient induces and control the crystallization of the macromolecule. In operation, a temperature ramp from a start temperature to an end temperature is used to maintain and control the temperature gradient.