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 together with our latest released version, 2021.1!