As the largest producer of cork in the world, Portugal has seen a wide range of projects directed at coming up with new applications for this ecological material. Cork is a natural material derived from the cork oak tree. It has a history of use dating back for thousands of years, and as with so many natural products, it is proving to have a wide range of applications in the modern world. Simply put, cork is the outermost layer of bark of two different species of oak tree that grow in the Mediterranean and Iberian region. It is harvested when the tree reaches 20 years, and then every 9 years after that. The productive life of the tree averages is about 150 years.