Twistronics is a newly born and rapidly growing field in condensed matter physics that studies how electronic properties of stacked single-layer van der Waals (vdW) materials, e.g. graphene, are affected when applying a twist between the layers. When single-layer vdW materials are stacked on top of one another with a small twist in orientation, the resulting structures may exhibit patterns with periodicity much larger (tens of nanometers) than that of a typical bond-length (angstroms); these patterns are known as moiré patterns. The new moiré length scale leads to interesting emergent physical phenomena. For instance, a graphene bilayer with a twist of 1.1° exhibits flat electronic bands, strong electron correlations, magnetism and superconductivity which are all absent in the constituent monolayer. However, at the moiré scale, the large number of atoms in these systems can make their accurate simulation very challenging, necessitating the development of efficient multiscale methods. In this seminar, I will first give an overview of the field and a brief description of popular moiré materials and their properties, and then I will present a recently developed multiscale approach to efficiently model both the atomic and electronic structures of these materials.