Broad review on models for porous media. In the choice of model, a marriage between pragmatism and sophistication is advocated, while keeping the application in mind. The ‘best’ model depends on the application, information available from characterisation and on how the porous material was created. Continuum models, discrete models for the solid and pore network models are discussed. Atomistic information can be included in hierarchical simulations. Advances in computing and characterisation underpin more accurate models. Chapter 3 focuses on porous media, to describe mass transport and reaction. A wide literature spanning physics, chemical engineering, earth sciences, etc. is referenced.