Optical evidence for PAMs. Confocal laser beam microscopy of a plasma membrane fraction isolated from 2 month-old Arabidopsis thaliana, transformed with green fluorescent protein (GFP) tagged to the ER lumen . The isolated plasma membranes were subjected to a repeated cycle of freezing and thawing to invert a population of the vesicles  and incubated with the red fluorescent probe FM4-64. The sample was observed under a 488 nm laser which excited the plasma membrane-localized probe (left image) and under a 543 nm laser which excited ER-localized GFP (middle image). To the right, these two images are merged.