Destabilization of membranes can occur as the result of physical stress (e.g., electrofusion) or chemical interference (e.g., polyethylene glycol). Electrofusion utilizes short pulses of electricity to mechanically disrupt the lipid bilayer of a cell to form pores and if two disrupted membranes come into contact, cell fusion may occur [29] . Unfortunately, this process is toxic and the cells must be in contact with one another at the time the electric field is administered. Laser trapping prior to electrofusion has been used to more effectively position fusion partners, however the process is low throughput and cytotoxic [30, 31] . A less toxic, but also less effective and less reproducible approach uses polyethylene glycol (PEG) [32, 33] . The exact mechanism of PEG-induced fusion is unknown but is theorized to be due to either local dehydration leading to unfavorable molecular packing of the bilayer or to dehydration of the "water shell" near the lipid bilayer, causing the water molecules between cells to be displaced, thereby forcing the two membranes together and subsequently fusing the cells [34] . This technique has proven useful, but fusion only occurs during the time of administration of PEG, thus cell delivery with PEG would induce fusion immediately and nonselectively. A mechanism that would better regulate fusion either to specific cells or specific regions within tissues is necessary to study fusion in vivo.