One of the UK's supermarkets is going to start charging customers for plastic bags in the latest effort to try to cut the number used.
Plastic bags may be handy for carrying stuff around, but campaigners say they're really bad for the environment.
Around 13 billion plastic bags are given free to UK shoppers every year. Each one takes 1,000 years to decay.
Marks & Spencer is going to charge food customers 5p for every bag - with the profits going to green charities.
It tried out the idea in some of its shops, and saw a 70% drop in the number of bags handed out.
The more bags we use, the more room we need to find to throw out all the old ones.
Often, they end up in places where animals live - causing big problems for them and the environment.
Plastic bags can end up in landfill sites
Cutting down on plastic bags isn't a new idea, with lots of towns across the UK trying to go plastic-free.
In Ireland, a 15p tax on plastic bags was introduced five years ago, which led to fewer bags being used.
But the people who count up all the things we buy say people bought more bin liners instead.