Redi's experiment on spontaneous generation, conducted in the 17th century, aimed to investigate the origin of maggots on decaying meat. He designed an experiment with two jars: one jar was left open while the other was sealed.
The purpose of leaving one jar open was to allow access to the surrounding air and the potential for flies to lay their eggs on the meat inside. The open jar represented the natural conditions where living organisms (in this case, flies) could interact with the decaying meat, thus leading to the appearance of maggots.
Conversely, the sealed jar prevented any access to air and, consequently, to flies. This setup was intended to illustrate that if flies could not reach the meat, no maggots would appear, thereby providing evidence against the theory of spontaneous generation—the idea that life could arise spontaneously from non-living matter.
By comparing the two jars, Redi concluded that maggots (and ultimately other life forms) did not spontaneously generate from the meat itself, but rather came from eggs laid by flies. His experiment laid important groundwork for the development of the germ theory of disease and further studies related to biogenesis.