Topological Density and Instantons on a Lattice

We present an update on the study of topological structure of QCD. Issues addressed include a comparison between the plaquette and the geometric methods of calculating the topological density. We show that the improved gauge action based on sqrt(3) blocking transformation suppresses the formation of topologically charged dislocations with low action. Using a cooling method we identify the instantons' location, estimate their size and density, and calculate the renormalization constant Z_Q for the plaquette method.