Moynul et al have published the paper entitled with ” Effect of Membrane Tension on Transbilayer Movement of Lipids, ” (J. Chem. Phys., 148, 245101, 2018) [Abstract] [PDF] . In this paper, we developed a new method to measure the rate constant of the transbilayer movement (fiip-flop) (kFF) of fluorescent probe-labeled lipids using single GUVs. Using this method, we found that the kFF greatly increased with tension without leakage of water-soluble fluorescent probes from the GUV lumen (i.e., without the formation of pores in the GUV membrane). We discussed its mechanisms.