Invariants of graphs in three-space

By associating a collection of knots and links to a graph in threedimensional space, we obtain computable invariants of the embedding type of the graph.Two types of isotopy are considered: topological and rigid-vertex isotopy.Rigid-vertex graphs are a category mixing topological flexibility with mechanical rigidity.Both categories constitute steps toward models for chemical and biological networks.We discuss chirality in both rigid and topological contexts.