At a mere 10,000 years old, tundra is the world's youngest biome, or ecosystem. Low temperatures, short growing seasons, and permafrost inhibit tree growth. The bare, rocky ground supports only mosses, heaths, and lichen. Tundra comes in three varieties: Arctic, Antarctic, and alpine (which occurs around the world at high enough elevations). You can use simple materials to recreate the frozen majesty of the tundra in a shoebox.