In this paper we introduce nanoscale description of fracture in a single crystal in order to obtain foundations for modelling damage at more averaged scale. Nanoscale model of fracture is discussed together with nanoscale model of slip plasticity. Fracture systems and slip systems are introduced consistently by means of free energy. They enable us to express critical conditions for initiation of both crack and slip. Evolution equations which describe evo- lution of crack, slip and boundary of slip surface are introduced. Furthermore, we also discuss crack initiation and propagation on active slip surface. With the aid of variables characterizing damage at nanoscale level we discuss the form of damage tensor for more averaged model. One discusses larger context of nanoscale modelling in which the nanoscale models are considered as a segment of multiscale description of behaviour of materials.