3 years & up. These amazing plastic sheets from Panelcraft® remain dark except for a 10-degree temperature range. Place a warm object on one, like your hand, and the color changes from brown to red, red to green, green to blue, and finally back to black again! The Heat Sheet empowers children to explore concepts of heat and light energy in their surroundings. Use alone or you can build a Heat Sheet Panel into the Panelcraft® Rainbow Solids Set (item #63546) and explore thermal conduction just like the pros! Each sheet comes with adhesive backing, for easy installation in the frame side of a Rainbow Solid panel. Activity Guide is included. Set of 5 sheets.