How did Louis Pasteur’s experiments support the principle of biogenesis?

Louis Pasteur’s experiments were pivotal in refuting the long-held belief in spontaneous generation—the idea that life could arise from nonliving matter—and establishing the principle of biogenesis, which holds that living organisms can only originate from preexisting life.12

Pasteur utilized "swan-neck" flasks to conduct his research. He filled these flasks with beef broth and boiled the liquid to sterilize it. The unique design of the flask featured a long, curved neck that allowed air to enter but trapped dust particles and other potential microbial contaminants in the bend, preventing them from reaching the broth.1

As long as the broth remained isolated from these trapped contaminants, it stayed sterile, demonstrating that life did not spontaneously generate within the nutrient-rich medium. However, when the neck was broken or the broth was exposed to the air containing particles, microbial growth occurred. By proving that microbes only appeared when introduced from the outside, Pasteur provided conclusive evidence that life arises solely from preexisting life, a finding that became a cornerstone of modern bacteriology and microbiology.12