While others, like Francesco Redi and Lazzaro Spallanzani, had conducted experiments that challenged the theory, Pasteur's work was crucial in providing definitive evidence against it. He used his famous swan-neck flask experiment to demonstrate that microorganisms only grow in broth when exposed to the air, not spontaneously within the broth itself. This experiment effectively showed that life arises only from pre-existing life, not from non-living matter.
