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Francesco Redi
He was the first man that proved that spontaneus generation doesen't exist. In his experiment, he put on three jars a pice of meat, and covered them using different materials. The first jar didn't have a covering, the second one was sealed and the third one was covered using cloth netting. With this experiment, he proved that rotting meat didn't produce maggots. -
John Needham
Needham claimed that spontaneus generation existed, he proved his thoughts with an experiment that consisted of heatting broth to its boiling pont, to kill all the microorganisms, then put it into some flasks, when the broth cooled, he sealed them. He waited a little bit and he observed living organisms in the sealed broth. Then he concluded that spontaneous generation was real. -
Lazzaro Spallanzani
He did many experiments to prove that Needham was wrong. In one of this experiments, he puted the broth into the flask and then boiled them for a long time, to kill all of the microorganisms. After some time he saw that the broth didn't have any trace of life. But once he unsealed the flask, microorganisms reapeard. He concluded that spontaneous generation was false and microbes came from contaminated air. -
Louis Pasteur
He recreated the experiments of broth, but he used flasks that had curved ends. He puted the broth inside the bottle, then he boiled them, to kill all of the microorganisms. For over a year he didn't observe any type of life inside the flask. But when he broke the neck of the bottle or titled the flask, he observed that in a few days there was life inside the broth. He concluded that the contamination came from life forms in the air, not from a "life force".