A computational technique based on theoretical knowledge of molecules to understand their behaviour. The theoretical models typically involve treating atoms as individual particles but can also include the modelling of the electrons of each atom. The interactions of atoms are described as spring-like interactions. The Lennard-Jones potential is often used to describe van der Waals’ forces. While simple calculations can be performed by hand, the complexity of the interactions between molecules requires powerful computers to undertake the necessary number of computations. Molecular modelling is used in the design of pharmaceutical drugs, material science, enzyme catalysis, and other areas of study requiring the understanding of the behaviour of complex molecular systems.