This lecture introduces the concept of coarse-grained simulations, which simplify complex systems by grouping atoms into particles. It explains the advantages of coarse-graining, different coarse-graining schemes, and simulation types. The lecture covers the DPD algorithm, including non-bonded and bond forces, integration methods, and practical examples of coarse-graining lipid membranes. It also discusses the importance of setting interaction parameters in DPD simulations and determining time and length scales for lipid bilayers.