According to homework help, the purpose of observing onion skin dripping water is to maintain the normal morphology of observation cells. When making temporary slices of onion skin, drop a drop of water in the center of the slide to keep the normal shape of cells. Because onion epidermal cells are completely immersed in clean water, they can avoid water absorption and bursting, and the normal morphology of onion epidermal cells can be seen during observation.