ELI5: Why are some ceramics dishwasher safe but not microwave safe?

and what will happen if I microwave them?

I recently got a very cute ceramic mug. It’s a skull and it’s got different colors of glaze on it. White, black, lime green. It says it’s dishwasher safe but not microwave safe. This is a bit of a bummer because I drink my second cup of tea in the morning very slowly and find I need to heat it up halfway through.

My theory is it has to do with the glaze, perhaps? Modern dishwashers, mine included, get very hot to sanitize, so I’m thinking the warning isn’t heat related. So why are some ceramics safe for a dishwasher but not the microwave. What would be the consequences of microwaving them? Will they crack? Turn the glaze toxic or something?