Liposome vesicles. Coloured transmission electron micrograph (TEM) of negative stained liposome vesicles. These artificially-constructed, spherical vesicles possess a selectively-permeable wall that closely resembles the membrane of a living cell. They are used in biotechnology research to investigate the functioning of the cell membrane and, since they can be incorporated into living cells, are used to deliver drugs of high toxicity to specific cells in the body, such as cancer cells. Each liposome is approximately 60-100 nanometres across.