Trees with different types and sizes of crowns create different horizontal layers known as [[1]] in the forest. 

Trees with different types and sizes of crowns create different horizontal layers known as understoreys in the forest. 

Giant and tall trees form the top layer or canopy, while the shorter trees form understoreys. The shrubs, tall grasses, and herbs together form the lowest layer in a forest. The canopy leaves intercept the sunlight making it dark inside the forest.