We report a new way of producing microcapsules consisting of a shell of aggregated colloids (also referred to as colloidosomes) using aqueous phase-separated polymer solutions (water-in-water emulsions) as a template. The extremely low interfacial tension of the template allows the production of reversible colloidosomes that spontaneously disintegrate depending on environmental conditions, making them ideal for controlled release purposes. Also, colloidosomes can have an elongated shape such that they may be used as microfluidic membranes or artificial arteries. Because the method described here does not use any organic solvents, it enables the use of sensitive materials such as cells and proteins.