A tree trunk is the sturdy, cylindrical structure that forms the main support and foundation of a tree. It serves as the central axis from which branches, leaves, and roots grow. The tree trunk is composed of layers, including the outer bark, inner bark, cambium layer, sapwood, and heartwood. It provides structural integrity to the tree and transports water, nutrients, and sugars between the roots and the canopy. The tree trunk often exhibits unique patterns, textures, and colors, reflecting the species and age of the tree.