Okay, so imagine you have a toy that you really like, but it's really big and you want to make it smaller so you can play with it more easily. You could try cutting it with scissors or a knife, but that might not work very well and you might ruin the toy.
That's kind of like what cryogenic grinding does, but instead of a toy, it's used for grinding up things like food, spices, or plastic into really tiny bits. Cryogenic grinding is a special way of grinding things that uses really cold temperatures to freeze the thing you want to grind, and then break it up into tiny pieces.
Here's how it works: imagine you have some ice cream that you want to turn into really tiny bits. If you just tried to smash it with a hammer or something, you'd squash it into a messy blob. But if you put it in the freezer first, it would get really hard and you could break it up into tiny pieces more easily.
With cryogenic grinding, you do the same thing but with things that aren't ice cream. First, you put the thing you want to grind into a special machine that uses liquid nitrogen (which is super-duper cold!) to chill it down to really low temperatures. This makes the thing very hard and brittle, like a frozen toy or ice cream. Then, you put it into another machine that grinds it up into really tiny pieces, like dust or sand.
So cryogenic grinding is a way to make things really small by using really cold temperatures to freeze them first, and then breaking them up into tiny pieces that can be used for lots of things.