What was the problem in Francesco Redis experiment?

Francesco Redi's experiment, conducted in the 17th century, aimed to refute the theory of spontaneous generation, which posited that living organisms could arise from non-living matter. The problem in his experiment was primarily related to the design; while he demonstrated that maggots did not appear on meat that was covered, critics argued that the meat was not exposed to air, which they believed was essential for life to generate. This led to a debate about the necessity of air for spontaneous generation and highlighted the need for controlled experiments to conclusively test scientific hypotheses.