Cork, also known as phellem, is a kind of outer skin product of Mediterranean oak. It’s the surface protective tissue of the stem and root after rough growth. Ancient Egypt, Greece and Rome used cork to make fishing nets floating, insoles, bottle plugs, etc.

The records of cork date from the Spring and Autumn Period of China. The main species of cork production are cork oak and Quercus variabilis. Usually, the first stripping can be carried out for oak with a diameter of more than 20 cm and no less than 20 years old. The skin obtained is called the cephalic skin or primary skin. After that, the skin is to be obtained every 10-20 years, which is called recycled skin, and the thickness of the skin is more than 2 cm.

The biggest use of cork is to be made into a variety of bottle plugs. Some of them, with the exquisite hot-stamping colorful patterns, become an endearing handicraft. It is said that the wine covered with this kind of bottle plugs is still fragrant after hundreds of years in the cellar.

Cork is flexible, air-tight, waterproof, adiabatic, non-conductive, and can withstand pressure and acid, so it has a wide range of applications. Spacecraft can use it as insulation material; Badminton seat, musical instrument gasket, high heel shoes, hat lining and other places can also see its trace; For floor made of cork, the trample has no sound, etc.

Portugal has always been known as the "Cork Kingdom", and its cork planting area accounts for 1/3 of the world's cork forest area, and cork is their traditional export commodity. It is worth mentioning that the whole cork tree does not all consists of cork - only the cork layer - the outermost side of the trunk is cork, while the innermost layer is the xylem, and the middle layer is the regeneration part of cork. Cork tree cannot be skinned until it’s 25 years old.