It has been theoretically and experimentally shown that the evolution of micro-scale domains in Lo/Ld phase-separated GUVs is mainly controlled by line tension, resulting in particular in domain coalescence, growth and budding (Figure , top). Based on that knowledge, we attempted to control the domain localization, growth, and coalescence by confining individual GUVs in microchannels to create free curved regions at specific positions (Figure , bottom). fuse and bud to reduce the line tension between co-existing phases, but this process occurs at random positions. In contrast, we envisage that, under physical confinement in a microchannel (bottom), domains preferably accumulate and fuse at the free curved regions, resulting in a domain localization at this specific position.