Embedded boundary Cartesian grids have greatly simplified the grid generation process for complicated engineering geometries. This approach to mesh generation uses a background regular mesh and takes special care of cut cells where the geometry intersects the grid. Grid generation is fast and robust. This chapter gives an overview of cut-cell grids. We discuss mesh generation and data structures used for implementation. We describe some stable and accurate discretizations for the small irregular cells that occur at the boundary. Much of this technology is mature and forms the basis for widely used CFD packages. Some possible directions for future research are presented.