Concrete  and  fibre  reinforced  concrete (FRC) have highly heterogeneous, nonlinear mechanical  properties due to the random  distribution of multiple phases at micro/meso-scales, which in turn determine the  performance  and  reliability  of structures at the macro-scale. In this  talk, we will review our recent efforts towards high-resolution characterisation of damage and fracture in concrete and FRC using the in-situ micro X-ray computed tomography (CT) technique, and CT-image  based  3D  mesoscale  finite  element  modelling and direct validation of  complex  nonlinear  fracture. Both continuous damage plasticity models and discrete crack models will be presented, with associated challenges discussed.