A Terrarium is kind of like a mini garden. You need Soil, Water, and Seed...but some people like bugs to help the Soil. We put icopods in our Terrarium. The seeds we used were Barley, Pea, Radish, Clover, And Corn. We put saran wrap over the top so the water would evaporate and then rain back down so we wouldn't half to water it daily. After a couple weeks we looked and measured out plants. Our longest plant was about 4-6 inches