Buzzfeed made a video where they took seven hamburgers from different restaurants, and put them in glass jars for 30 days to see how moldy they'd get.

The burgers are from McDonald's, Burger King, Wendy's, Carl's Jr., Jack in the Box, In-N-Out, and an L.A. chain called Umami Burger. They time-lapsed the video, and it's pretty gross to see some of the results.

The weird thing is that a few of the burgers, like McDonald's and Jack in the Box, didn't get very moldy. (McDonald's actually addresses this on their website.)