The Unemployed Philosophers Guild Disappearing Dino Mug - Heat Sensitive Color Changing Coffee Mug - Add Hot Liquid and Watch Dinosaurs Turn to Fossils Thanks to this clever Disappearing Dino Mug you can watch eons pass before your eyes over a cup of coffee. When you pour in a hot beverage, the dinosaurs transform into fossils in a museum exhibition. Disappearing mugs are not dishwasher safe but are microwave safe. Large mug, holds 12 oz.