Trees form one such class of directed graphs that have an inherent ... network has a tree structure and draws the network with the root at the left edge of the diagram and the children of each node ...

In the 12th century in Medieval Europe, we had all this information coming form the ancient world ... a collection of tree-based diagrams of science and human knowledge, published in 1296.

We know this because of a biological tool called the tree of life. This "tree" takes the form of a diagram that maps the relationships between plants, animals and other organisms. Its "trunk ...