Gratings are the most widely applied diffractive optics elements in various optical systems. VirtualLab Fusion software provides the Fourier modal method (FMM a.k.a. RCWA) and the thin element approximation (TEA) for grating simulations. This interactive online training shows how to use the corresponding technologies from VirtualLab Fusion to solve practical grating modeling and design tasks for modern optics applications. In the training, we will of course work with our latest released version, 2023.1! Learning outcomes: - Learn how to construct the grating geometry and materials; understand the basic theory of the modeling technologies and their differences; use the software tools for grating analysis and design. - Practice hands-on with selected rigorous modeling examples, including blazed grating, rectangular grating, slanted grating, holographic volume grating, and metagrating. - Design workflow discussed along examples, like moth-eye anti-reflection grating, waveguide coupling grating, polarization-insensitive pulse compressor grating, and beam-splitting metagrating.