Louis Pasteur (1860-1862) French):

Even after the experiments of Spallanzani, the conflict of a biogenesis and biogenesis continued well into the middle of 19^th century till Louis Pasteur famous for Germ Theory of Disease and Immunology finally disproved a biogenesis and proved biogenesis. He kept the sterilized syrup of an infusion of yeast and sugar in flasks and observed that a rich bacterial growth appeared in the syrup if it was exposed to air pollution. But no bacteria growth appeared in the flasks were either kept airtight of only purified air was allowed into them. How could Pasteur get pure air? For this he used a simple, but ingenious device, he heated the necks of some of his flasks and drew these into long shaped open tubes  When air entered  into these flasks, all  air borne particles, including spores, germs etc. Got  stuck at the bends of the tubes, so  that only pure air reached the syrup. Hence, the syrup remained sterile. This conclusively proved that even micro organisms never form spontaneously upon present earth.