Tin foil is a common household item that many of us use daily as we cook meals for ourselves and our families.
But a top chef has said we've been using it wrongly for years, with many people making the same common mistake.
Chef Tom Kerridge left people shocked when he explained how to use it properly during a segment on TV.
Last year Tom mentioned the tip on Fresh Start and it's safe to say he blew people's minds.
He revealed there's actually a right - and wrong - way to use it.
You'll probably use yours to wrap jacket potatoes, sandwiches and line your oven trays.
But the next time you buy a pack, you need to be aware of Tom's advice.
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He said: "There are two sides to tin foil, there's the shiny side and the not so shiny side.
"Always remember dull side up, shiny side down, it's the reflective side
"That's going to reflect as much heat back as possible
"Just cooks a little bit more efficiently."
And people quickly took to Twitter to share their astonishment.
One person said: "Shiny side down for tin foil!! Just literally said ‘i never knew that!’ out loud to the TV."
Another said: "Well! You learn something new EVERY day. Today’s is that shiny side on tin foil goes towards food and dull side goes up. Thanks @ChefTomKerridge Not sure how I’ve got to 52 without knowing "
And a third said: "Tom Kerridge on BBC2 just said tin foil always put shiny side down. I always have it shiny side up! Have I been doing it wrong all these years?"
