Two independent routes for traceable measurements of particle number concentrations through SAXS (Small Angle X-ray Scattering) and spICPMS (single particle Inductively Coupled Plasma Mass Spectrometry) will be developed for monodisperse materials. The sensitivity, linearity, size and material dependence of laboratory techniques will be determined and a full uncertainty budget for all methods will be produced, together with calibration procedures for techniques used by industry. The particle number concentration will be determined with a target uncertainty better than 10 %. Additionally, we will investigate methods capable of resolving multimeric particle populations with particles agglomeration levels ranging from 0 % to 50 % and develop methods for measuring the fraction of particles in agglomerated states using DCS (Differential Centrifugal Sedimentation) and SAXS. A quantitative framework that can rapidly and accurately measure both the shell thickness and its chemical composition will be developed using X-ray Photoelectron Spectroscopy (XPS). Methods to measure the concentration of surface functional groups on nanoparticles in situ will be developed using conductometric and potentiometric titration, as well as novel non-linear optical methods. The industrial relevant methods will be compared to accurate techniques like mass spectrometry, elemental analysis, NMR spectroscopy, and XPS The results of VAMAS (Versailles Project on Advanced Materials and Standards) interlaboratory studies will codify the best practice for industry in these areas and initiate new work items and contribute to emerging documentary standards in ISO. This will result in the generation of reference materials suitable for assessing the ability of laboratories to measure number concentration and shell thickness of spherical nanoparticles.