Hornets get the materials for their nests by chewing plant materials such as wood or bark and combining it with their own saliva to make a paper-like substance. This material is set into the eve of a structure that will allow enough support for the honey-comb shape in the top of the nest, and the paper begins to dry. As it does, the cellulose fibers interweave to hold the nest together. The nest is built from a top support down, in a series of hexagonal cells that create the distinct honeycomb. Nests will expand as needed, with new cells added as the colony grows.