I am currently trying to understand Grothendieck Topologies and coverages and want to endow the category Prob, consisting of finite probability spaces and measure preserving maps, with a Grothendieck Topology. I have already tried endowing it with the trivial topology and dense topology but got no interesting results (yet). Is there an interesting topology that can be put onto Prob, or is there a general way to endow a given category with an interesting Grothendieck Topology?