The majority of plants in the Amazon rainforest are trees. Tropical rainforests have more types of trees than any place in the world; scientists have counted 100 to 300 species in one 2 1/2-acre area in the Amazon rainforest. The trees form four separate areas in the rainforest, including emergent trees, the canopy, the understory and the forest floor. Emergent trees are umbrella-shaped trees with smooth bark that are 100 to 240 feet tall. The upper canopy has 60 to130 feet tall trees and most of the rainforest's animals live in the upper canopy. The understory, or lower canopy, is shaded by the upper canopy and contains shrubs, plants and trees up to 60 feet tall. The forest floor is so shaded that few shrubs can grow there; a shrub/sapling layer on grows on the forest floor, however it receives very little light that filters through the canopies, and hence, has some stunted growth.