Parts of the Leaf 3-Part ReadingA leaf's main job is to absorb sunlight and you can just feel the sunlight in this leaf from the river beech tree. Look carefully at these cards and discover each of the key parts of a leaf's external anatomy. The photos include the featured part in full color while the rest of the image fades into muted shades of gray. For the first time, it is really clear what we want them to focus on!