DID your mum always pull a face when you told her the piece of toast that had slid off your plate and landed on the kitchen floor was still okay to eat because of the 'five second rule'?
Well now you can tell her the theory food is still okay to eat if it's picked up within seconds of hitting the deck is true.
Germ expert Professor Anthony Hilton, from Aston University, said that although retrieving these morsels can never be completely without risk, there is little to be concerned about if the food is only there momentarily.
Prof Hilton will be demonstrating how the five-second rule works at The Big Bang Fair - a celebration of science, technology, engineering and maths (STEM) for young people - which opens on Wednesday at the NEC in Birmingham.
He said: "Eating food that has spent a few moments on the floor can never be entirely risk-free.
"Obviously, food covered in visible dirt shouldn't be eaten, but as long as it's not obviously contaminated, the science shows that food is unlikely to have picked up harmful bacteria from a few seconds spent on an indoor floor.
"That is not to say that germs can't transfer from the floor to the food.
"Our research has shown that the nature of the floor surface, the type of food dropped on the floor and the length of time it spends on the floor can all have an impact on the number that can transfer."
It comes as a survey of 2,000 people found 79% admitted to eating food that had fallen on the floor.