Francesco Redi was an Italian physician that was among the first to disagree with the idea that maggots could spontaneously generate on meat left out for extended periods of time. To disprove the idea of spontaneous generation he did an experiment using raw meat and flies. 2 jars of raw meat were left exposed to air, 2 covered in gauze, and 2 tightly sealed. His theory was that if flies could not reach the meat, then maggots would never develop. He was proven right when no maggots appeared in the covered jars.