PACS 100 and 160 μm differential number counts, normalized to the Euclidean slope (dN/dS ∝ S^-2.5). Filled and open symbols show flux density bins above and below the 80% completeness limit, respectively. Grey shaded areas present estimates obtained using pre-Herschel observations. Blue shaded areas present estimates obtained using PACS observations (Berta et al. 2011). Lines represent predictions from backwards or forwards evolutionary models (Lagache et al. 2004; Rowan-Robinson 2009; Valiante et al. 2009; Le Borgne et al. 2009; Franceschini et al. 2010; Gruppioni et al. 2010; Lacey et al. 2010; Marsden et al. 2011; Rahmati & van der Werf 2011; Niemi et al. 2012; Béthermin et al. 2012).