Here's an #adulting tip: If you ever have a food stain that won't seem to go away, try applying an ice cube to it. This miracle on ice works with both fresh and set-in stains.
Although, we're often taught that hot water, detergents, and scrubbing are the ways to get clothes clean, there are a few exceptions. Protein stains are one of them. There is a certain temperature range in which soils, like tomato stains, can get "baked" onto laundry. Though it varies from stain to stain, generally cold is good.
Ice lets you reconstitute stains without the risk of denaturing the proteins. Denaturing is a fancy word for "taking apart." It's basically how cooking works–breaking down food to make it easier to eat. But easier to eat doesn't mean easier to clean. Think of it this way: It's easier to pick up a single sheet of paper off the floor than a handful of confetti.
So, the next time you get some ketchup on your shirt, put it on ice. When you do, you'll be able to tell everyone around you why it works.