Mesosomes or chondrioids are folded invaginations in the plasma membrane of bacteria that are produced by the chemical fixation techniques used to prepare samples for electron microscopy.These structures are invaginations of the plasma membrane observed in gram-positive bacteria that have been chemically fixed to prepare them for electron microscopy. They were first observed in 1953 by George B. Chapman and James Hillier, who referred to them as “peripheral bodies.” They were termed “mesosomes” by J. D. Robertson in 1959.Most microbiologists will argue that mesosomes do not exist. They are likely an artifact of the preparation process for electron microscopy since they cannot be observed in “non-fixed” samples.However, as their existence is debatable, those who believe in their existence state that they are the infoldings in the plasma membrane, they are rich in enzymes that helps to perform functions like cellular respiration, DNA replication, secretion of glycocalyx and cell division (most important function; it increases the surface area of the cell membrane.)\xa0