Chemists routinely use atoms that can form directional bonds to assemble complex and useful molecular structures. But larger colloidal particles have proved less conducive to rational assembly because they lack specific directional bonds. David Pine and colleagues now report a way around this problem that could lead to the creation of a rich variety of new micro-structured colloidal materials with technologically useful properties. Using microsphere clusters as intermediates, they create colloidal particles with chemically distinct and precisely located 'sticky patches' on the surface — up to 7 per particle — that enable specific and highly directional bonding. Using this system, they assemble 'colloidal molecules' exhibiting a wide range of bonding symmetries.