The improvement of microscopes allowed scientists to observe microorganisms directly, proving that life comes from existing life, not from nonliving matter.ExplanationBefore microscopes, people believed in spontaneous generation — the idea that living things like maggots or mold could just appear from rotting food or other nonliving material. With better microscopes, scientists like Anton van Leeuwenhoek could clearly see tiny organisms, and later, experiments by Louis Pasteur showed that these microorganisms came from other microorganisms in the environment. This direct observation helped scientists prove that life does not spontaneously appear but is the result of reproduction from existing life forms.