Stronger than plastic and tougher than glass, the resin-filled material is being exploited for smartphone screens, insulated windows and more. Wood is made up of countless little vertical channels, like a tight bundle of straws bound together with glue. These tube-shaped cells transport water and nutrients throughout a tree, and when the tree is harvested and the moisture evaporates, pockets of air are left behind. To create see-through wood, scientists first need to modify or get rid of the glue, called lignin, that holds the cell bundles together and provides trunks and branches with most of their earthy-brown hues. After bleaching lignin’s color away or otherwise removing it, a milky-white skeleton of hollow cells remains.