*9.1.1 Vesicle shape, size and morphology*

The liposomes physical stability depends on their size and polydispersibility index [72]. The size is important in parenteral formulations [73]. Electron microscopy is used for measurement of liposome vesicle size and determining their morphology and lamellarity [74–76]. Transmission electron microscopy (TEM) is mostly used in measurement of size distribution. Cryo transmission electron microscopy helps in visualizing liposomes that are in frozen state [77]. This is advantageous because analysis is done at their storage environment and prevents disruption of vesicles [78]. Liposomes are applied in a thin film form to a grid and that grid is to be kept in cooling medium (mostly liquid nitrogen) and viewed under microscope and imaged [79, 80]. This microscopy method is advantageous because vesicles can be measured individually which gives detailed information in size and matrix [81, 82].
