This book contains lecture notes of current development in multiscale modeling, computations and applications. It covers fundamental mathematical theory, numerical algorithms as well as practical computational advice for analysing single and multiphysics models containing a variety of scales in time and space. Complex fluids, porous media flow and oscillatory dynamical systems are treated in some extra depth, as well as tools like analytical and numerical homogenization, fast multipole methods and wavelets. The text includes well designed exercises and project reports on different applications such as astrophysics, computational chemistry, porous media flow and climate change.