The hexaiodobenzene molecule shown in the image, when deposited on a noble metal substrate such as Cu(111) , Ag(111) or Au(111), at room temperature looses the I atoms and starts diffusing. The relative probability of diffusion and of binding to a neighboring molecule determine the shape of the network that will be obtained. The experiments performed at Empa [ http://dx.doi.org/10.1021/ja107947z J. AM. CHEM. SOC. 2010, 132, 16669–16676 ] shows that on a Cu substrate dendrites will form while on a Au substrate 2D networks will form. The python program KMC.py will allow you to simulate the diffusion and binding of molecules once the energy barriers for the diffusion event and for the binding event as well as the simulatin temperature will be defined. During the execution the program shows snapshots of the positins of the molecules. Molecules free to diffuse will be represented via blue dots. Molecules that irreversibely formed a bond with a neighboring molecule will be represented by red dots.