Artificial particulate systems Such as lipid vesicles are found in a variety of biomedical applications such as drug delivery and targeting. More versatile layers of control would be added if liposomes could be glued together on demand while stabilized against fusion. Here, we present a two-component molecular glue composed of a protein and calcium ions, with each component specialized for fast and specific binding to negatively charged lipid membranes. Upon mixing the two components, the high affinity binding of this glue starts to tightly bridge two lipid vesicles on a subsecond scale. Furthermore, highly charged liposomes are beneficial in preventing spontaneous fusion before applying the molecular glue.