In the mid-18th century, Needham conducted experiments with broth that he boiled and then sealed in flasks. He observed that after a few days, the broth became cloudy, indicating the presence of microorganisms. He concluded that the microorganisms had spontaneously generated from the broth itself.
However, Needham's experiments had flaws, as his boiling process wasn't sufficient to kill all existing microorganisms, and his seals were not airtight. Later experiments by Lazzaro Spallanzani, and later, Louis Pasteur, disproved Needham's theory and provided evidence against spontaneous generation.
