Both fluorescence loss in photobleaching (FLIP) and the related methodology of recovery after photobleaching (FRAP) are techniques for observing the movement of intracellular materials through photobleaching of fluorescence. A floating fluorescent dye evenly distributed on a cell or organelle membrane(endoplasmic reticulum and Golgi apparatus), or a floating fluorescence-labeled protein on these membranes is bleached in a small circumscribed area, and the loss or recovery of fluorescence is observed to examine fluidity in the lateral direction. The techniques of FLIP and FRAP are also used to confirm the continuity of membranes.