There's no doubt you've heard of "the five-second rule": if you pick food off the floor within five seconds, it's okay to eat.
Scientists from Rutgers University in the United States put the infamous theory to the test and found that isn't true.
Proponents of the five-second rule reckon it works because bacteria takes time to transfer.
However, the scientists found that all depends on moisture, surface type and contact time.
They discovered bacteria actually transfers to food in less than five seconds and in some even less than one second.
They tested watermelon, bread, butter and gummy candies on four surfaces - stainless steel, ceramic tiles, wood and carpet.
Unsurprisingly, watermelon had the highest level of contamination.
That's because germs are more easily transferred through moisture, whereas dry gummy bears had the least bacteria.