Sapwood is the living wood in a tree. It is found between the inner bark and the heartwood of the tree. Sapwood ensures the upward sap flow and serves as a storage place for nutrients. It has exactly the same structure as heartwood, but a different chemical composition: it does not deposit the substances that protect the heartwood and is always light in colour. Depending on the growing speed of the wood type, sapwood may be more or less visible on wooden planks. A stripe with a shade lighter than the rest of the plank can then often be seen.