Polymer encapsulated particulate material that is 100 microns or less in size, wherein: (a) said particulate material is encapsulated in a substantially uniform and continuous coating of a polymer which has at least in part been formed under the control of a RAFT agent; or (b) the polymer which encapsulates the particulate material has at least in part been formed under the control of a RAFT agent, and wherein the particulate material is substantially uniformly dispersed throughout the polymer.