Cycles are supported through bridges. A bridge consists of two bond-node pairs that together represent one bond. On each side of a bridge an atom connects to a bond, but the two atoms are not connected to each other. Instead, each atom is succeeded by a bridge node. Unlike an atom, a bridge node has no children and so may not serve as the root of the tree. A bridge preserves the A parent atom can be connected to a child atom through a bond (left). A parent atom can also be connected to a child bridge node through a bond (center). Finally, an atom can be connected, without bonding, to a child atom through a gap (right).