The course is an introduction to the techniques of molecular modelling in the field of molecular systems of biological interest. The student, at the end of the course, will know the main computational methodologies to study the structure and the energetics of small to large molecules. In addition to the formalism and the theoretical foundations of such methodologies, the students will also learn how to use them to determine structural, spectroscopical, chemical properties of molecules. These experiences with computational simulations will allow the students to rationalize and interpret data coming from experimental measurements or from other simulations so to have a more complete picture of limits and potentialities of the most common computational approaches to study biological systems.