Sameer Kher starts us off with a discussion on the important topic of simulations. Simulations have been used for years in modeling and design. More recently, they have become a core aspect of digital twins, simu­lating outcomes during design phases and in using real data during operations. Kher describes the phases associated with applying simulation in digital twins as well as use of simulation in areas such as predictive maintenance. He concludes with describing how you build, validate, and deploy a simulated digital twin.