Review on The Unemployed Philosophers Guild Disappearing Dino Mug - Color Changing Coffee Mug for Dinosaur Lovers - Heat Sensitive - Watch Dinosaurs Transform into Fossils! by Andrew Griggs

Works - sort of yes. But only if you use boiled water. I bought this fir tree for my son's birthday and when we made hot chocolate today it didn't change. I was just as disappointed as he was. I tried doing it under our hot water and it barely worked. I have to run it on the outside of the cup to get the change. The water is too hot to put my hands under while I walk, but I don't know the exact temperature. So I filled the cup hoping the cup would get hot but instead the color image came back in less than 30 seconds. I finally tried boiling hot water and it worked, unfortunately it's too hot for anyone to drink from to get the benefits. Pretty lazy about it.