During the time that Gregor Mendel conducted his experiments little was known about the structures of the cell and cell division. In fact, Mendel was not totally sure of why he got the results that he found. He formulated the hypothesis that an organism’s traits were controlled by particular factors which were passed on by the parents. It wasn’t until after the invention of the microscope and subsequent studies of the cell’s anatomy that Mendel’s work was rediscovered. Chromosomes were stained and made visible which made it possible for scientists to clearly observe the processes of mitosis and meiosis (cell divisions). Assumptions were then made that the chromosomes carried the heredity factors.