Cork is an impermeable buoyant material. It is the phellem layer of bark
tissue which is harvested for commercial use primarily from Quercus suber
(the cork oak), which is native to southwest Europe and northwest Africa. Cork
is composed of suberin, a hydrophobic substance. Because of its impermeable,
buoyant, elastic, and fire retardant properties, it is used in a variety of
products, the most common of which is wine stoppers.
The montado landscape of Portugal produces approximately half of the cork
harvested annually worldwide, with Corticeira Amorim being the leading company
in the industry. Cork was examined microscopically by Robert Hooke, which led
to his discovery and naming of the cell.