Thermochromic mugs

Thailand ... and it is King Bhumibol Adulyadej 82nd birthday ... December 2009 In Chiangmai there was an open market on for 10 days and inside the market I found a stall from Doi Tung Top Tea. One of the attractions to the stall was the thermochromic mugs they had for sale ... pour in hot water and the image on the outside changes ... they were Chinese images (not Thai) .. but still fascinating. I knew that all that chemistry learnt in school would mean something eventually ;-)