This has quickly become one of our all-time favorite items. Just place the tiny (2mm) spheres into a bowl of water and allow them to sit overnight. In the morning, you will be treated to over 5 cups of gel-like clear spheres! They not only look cool, just wait until you feel them. Then comes the amazing part as you drop them back into water and they seem to disappear. You can even color the spheres by expanding them in water with your own food coloring.
Students are really fascinated by these and they teach about super-absorbant polymers, light refraction, and generally fascinating science. Makes a great giveaway for science birthday parties. Contains a pack of growing spheres, a reusable plastic test tube, and instructions.