small holes. The competition for space results in a fine-meshed polygonal network of nanoparticle deposits. The concentration of particles is much higher at the network nodes – an effect that can not been seen within the KMC model. As the particles attract the liquid there remains some liquid on the substrate where the nanoparticles are. Fig. 5 gives snapshots of the evolution of a fingering instability for a retracting dewetting front. At early times the straight front shows a rather short-wave instability, about 16 wiggles can be seen. However, they are only a transient: the finger pattern coarsens rapidly till only about 7 fingers remain. The fingering then becomes stationary, i.e., just as in the KMC, the mean finger number remains constant, although new branches are continuously created and old branches join each other. In general, the results on fingering agree well with results obtained using the KMC model [41]. From this we conclude that jamming of discrete particles is not a necessary factor for causing the instability, since the fingering is seen here in a continuum model with a diffusion constant that is independent of the nanoparticle concentration. The DDFT is better suited than the KMC for investigations of the early instability stages: they are more easy to discern without the discrete background noise of the KMC. Furthermore, one may perform a linear stability analysis of the one-dimensional undisturbed streamwise front profiles with respect to transverse perturbations (in analogy to the approach used in Refs. [19, 86, 87]). The previous two sections focused on two approaches to describe the experimentally observed patterning dynamics in the ultrathin postcursor film left behind by a mesoscopic receding dewet- ting front. Although both the kinetic Monte Carlo model and the dynamical density functional theory are able to describe well the processes in the ultrathin film, they can not be employed to describe mesoscale hydrodynamics. A relatively simple model for the latter can be derived in the framework of a long-wave or lubrication equation [8, 63]. We will illustrate here the approach by considering an isothermal situation where the nanoparticles are not surface active, i.e., they do not act as surfactants. For a model incorporating the effects of latent heat generation and surface- active particles resulting in thermal and solutal Marangoni stresses, see Ref. [88]. A description of spreading particle solutions incorporating a structural disjoining pressure has also been considered [89]. For related work on particle-laden film flow on an incline see Refs. [90, 91]. One starts from the Stokes equations, together with continuity, no-slip boundary conditions at the 18 C. Thin film hydrodynamics