One of the foundational results in extremal graph theory is the Erdos-Stone Theorem, which says that ex(n, H)=((X(H)-2)/(X(H)-1)+o(1))n^2/2 where ex(n,H)+1 is the minimum number of edges needed to guarantee that any n-vertex graph contains H as a subgraph. However, this theorem gives little information for X(H)=2. In this lecture we'll examine the Zarankiewicz problem, which considers the case when H is a complete bipartite graph. Speaker(s): Mia Smith (UM)