A large part of the solar corona is composed of bright arcs of confined plasma, the coronal loops. Far from being monolithic cylindrical structures, coronal loops have a finely structured and dynamic interior. With the help of 3D MHD simulations with MURaM, we investigate the energisation and structure of coronal loops in different magnetic topologies and model the resulting observable emission. Simulations with a sufficiently high resolution are necessary to resolve the large range of scales of motions at the solar surface that power the corona. We discuss the connection between different layers of the solar atmosphere and how photospheric motions at the loop footpoints determine the spatial and temporal scales of coronal loop heating.