(1914) defined cultures as “controlled” or “uncontrolled” in reference to the fact that in the former the histological and functional characteristics of the original organ were maintained, whereas in the latter tissue organization and functionality were lost. During the 1920s, research focused on embryology, especially limb morphogenesis, leading to the development of tube cultures (Strangeways and Fell, 1926) and the watch glass method, which consisted of a concave glass surface holding a plasma clot in its center over which the tissue fragment/organ rudiment was embedded and cultured. The watch glass was enclosed in a Petri dish carpeted with wet cotton wool (Fell and Robison, 1929). By the 1950s, many other organs had been cultured in vitro, but with the limitations imposed by these culture methods and the lens paper method, which allows the culture of thin organ slices (Trowell, 1954, 1955). Mostly researchers worked on avoiding the migration of cells from the tissue specimen, tried to optimize the gas exchange conditions, and reduce necrosis. In this same time frame, researchers started to analyze the regenerative capacity of dissociated cells. As early as 1907, Wilson (1907) showed that sponges could be broken down to single cells that were able to reassociate
