Molecular dynamics (MD) simulations are routinely used to study the structure and dynamics of biomolecules at the atomistic level. Even though the models are by their very nature wrong in many ways, they are useful in showing us atomistic details of phenomena which cannot be directly observed experimentally . MD simulations have led to advances in drug and enzyme design and material science, and they have greatly increased our understanding of the interactions of biomolecules at the atomistic level.