\OUTLINE: What is the crossing number problem? Why did it start? (see history – Turan’s brick problem) Actual answer is NP-Complete, however we can use good algorithms to find answers sometimes, and also find bounds quickly Complete bipartite graph – K(m, n), show examples below Inequality, show proof – using Euler’s formula and expectation Crossing number problem: cr(G), the crossing number of a graph G, is the lowest number of edge crossings in a graph. K(3, 3) (2 crossing: Petersen graph) - this shows the method for representing a complete bipartite graph with as few crossings as possible