The DSMC technique uses a finite set of model particles (simulators) that move and collide in a computational domain to perform a stochastic simulation of real molecular gas dynamics. The basic concept of the method is based on the discretization of time and space in the real gas dynamics process, and it splits the motion into two successive stages: free molecular motion and binary intermolecular collisions within the grid cells at each time step. In this chapter, the novel N-particle equation governing the DSMC technique is presented, and the principles of the DSMC method are described, with potential applications to MEMS filled with gas in mind. A preview of classic collision algorithms, including Majorant Collision Frequency, Bernoulli Trials, and No Time Counter, will be provided, with particular attention to their relationship to the Boltzmann equation, their corresponding accuracy, limitations, and restrictions. The application of different boundary conditions will be discussed. The simulation of near-continuum gas flows using time-relaxed and hybrid schemes will be presented. The simulation of low-speed gas flows is an essential microfluidic issue. Some new DSMC schemes for multiscale simulation will be presented. Finally, the simulation of gas flow in complex two and three domains will be commented on, and new DSMC algorithms using a small number of particles in cells will be described.