Cork is the outer protective layer of the bark of a tree, made up of dead cells that are rectangular-shaped and compactly arranged without intercellular spaces. Cork cells are one of the parts of the bark, made of multiple layers of cells. When the bark of plant cells becomes old, it will be replaced by a secondary meristem. The following are the important functions of cork cells:

• Prevent water loss from the plants, like epidermal cells.
• Protect the plant from various kinds of infections, especially fungal infections.
• Protect plants from various injuries.

Cork cambium is responsible for the secondary growth that replaces the epidermal tissue in young roots and stems. Cork cambium cells divide to form new cells that differentiate into either cork on the exterior of the cambium layer or phelloderm cells on the interior. New cork cells increase the depth of the cork layer as these cells are deposited behind older cork cells. The cork cells produced by the cambium have thick walls that contain suberin, a waxy, hydrophobic substance that serves as an impermeable protective barrier and prevents water loss.