text: In 1861 , Louis Pasteur performed a series of experiments which demonstrated that organisms such as bacteria and fungi do not spontaneously appear in sterile , nutrient-rich media .
simplified: Yet it was not until 1861 that Louis Pasteur performed a series of careful experiments . With these experiments , Pasteur proved that organisms such as bacteria and fungi do not appear in nutrient-rich media of their own accord in non-living material .