Intriguing toy/ token. Glass tubing contains a special volatile liquid that boils at just above room temperature - the warmth of your hand will make it boil! You cup the bottom bulb and in a few seconds the liquid boils up through the tubes; cup the top bulb and it boils back down again. This science toy had a lifetime as a 'love meter' - you demonstrate the warmth of your love. Very light box, 16cm tall. Tubing is glass, so fragile.