This is a demonstration of how to animate budding vesicles or fusing ones using the inheritance effector and simulation effects in Cinema 4D. In this animation I show both processes, but in actuality a vesicle does not bud from the same place another was absorbed. Also, there are many proteins involved in both vesicle fusion and vesicle budding, because alterations to the bilayer take energy. One of the type of proteins involved in vesicle fusion are SNARE proteins, which I've done a simple simulation of. Vesicle budding occurs through various processes, one of which is assisted by Clathrin proteins. A great animation by Janet Iwasa shows the current model of this mechanism. The budding process is also one that HIV hijacks to exit human cells and spread to other cells, in this case it uses the human ESCRT proteins to exit cells.