Molecular Structure of the Substance - Version 2.1 The educational program for the field of physics and chemistry, supported by simulations. This program is the type of a graphic simulation which is the most important element for the educational purposes. The program consists of nine sequences (substance classification, molecule motion, Diffusion, Brown's motion, temperature and pressure, ideal gas, real gas, crystal structures). At every simulation there is a possibility of continuous changing of certain parameters (temperature, volume).