In situ 3D characterization of Aquamarijn microsieves fouling was achieved using Confocal Laser Scanning Microscopy (CLSM). A filtration chamber allowing direct microscopic observation of particle deposition and cake characterization, specially designed for in situ observations, was used. Suspensions of fluorescent monodisperse spherical particle (1 mu m and 4.8 mu m) were filtered under constant flow rate through 0.8 mu m and 2 mu m pore diameters silicon nitride microsieves. On-line images of particle deposition were recorded and the cake build up was followed layer by layer. Based on 3D image processing, cake morphology (particle arrangement, homogeneity, thickness and porosity) was characterized and correlated to permeability reduction recorded during the filtration experiments. (C) 2013 Elsevier B.V. All rights reserved.