Our review paper Multiscale in modelling and validation for solar photovoltaics together with members of Multiscale Solar COST Action is published on EPJ Photovoltaics. The main aim of the Multiscale Solar networks is to explore the challenges in the implementation of next generation solar cell architectures that require novel multiscale modeling and characterization approaches. Such approaches capture both the peculiar features at the atomistic and nanoscale and their impact on the optoelectronic performance at device level. We have in this paper discussed ongoing trends and remaining challenges on the different length scales including active research directions in the network.