Louis Pasteur and Claude Bernard complete the experiment disproving the theory of spontaneous generation.

The theory of spontaneous generation was an early scientific hypothesis proposing that life could arise from non-living matter without any biological precursor. Rooted in ancient philosophy, it was widely accepted for centuries, with thinkers like Aristotle suggesting that creatures like maggots, frogs, or mice could originate from decaying meat, mud, or grain, respectively. This theory persisted largely due to observational misinterpretations—people saw life seemingly emerge from inert substances and assumed it was created spontaneously. However, the theory began to unravel with experiments by scientists like Francesco Redi in the 17th century, who demonstrated that maggots only appeared on meat when flies could access it. It was ultimately disproved by Louis Pasteur in the 19th century through his famous swan-neck flask experiments, which showed that sterilized broth remained free of microbial life unless exposed to contaminants in the air. This pivotal moment helped establish the germ theory of life and laid the foundation for modern microbiology.