Observe both a physical and a chemical reaction in this tasty experiment. You may have seen agate crystals used as a colorful home decorations, but it took many years for these rock formations to develop. Agate crystals are formed when microcrystals within a hollow pocket of a host rock begin self-organizing to form patterns. The colors and arrangements of the crystals are influenced by changes in temperature, pressure, and mineral content. Luckily, our experiment only requires a physical change by being crushed, a chemical change from the oven by being heated and melted, and it takes a lot less time to develop these crystals!