This item is, hands down (ha ha), one of Arbor´s most popular items. Though it looks like something one might find in Dr. Jekyll´s back room laboratory, the hand boiler is pure fun. Kids hold the hand boiler in the palm of their hand and wrap their fingers around the lower bulb. Then, they watch with amazement as the liquid migrates up the tube and into the upper bulb. Eventually, the liquid in the upper bulb will appear to "boil" as air is drawn up the tube.