I will study the property of Chaos with Magnetic Field in spin glasses. I will report the results for Spin Glasses on Random Regular Graphs and 4D lattices. I will compare the simulation with analytic predictions obtained generating random trees according to the Replica Symmetry Breaking theory. I will show that using the Overalp Probability function P(q) as input one can quantitatively predict the degree of decorrelation as the field increases. One can also compute the finite volume effects in the magnetization and the susceptibility as a function of the field.