TP1 will not be a stand-alone topic but will be integrated in all other activities in TP2-3 as well as contribute with direct input to TP4 illustrated in Figure 1 and in the distribution of tasks (Table 1). The characterization will include chemical analysis (atomic absorption spectroscopy (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES)), solubility and speciation determination, and particle morphology. Analysis of individual particles/aggregates will be conducted using electron microscopy based techniques (TEM, SEM-EDX). Disintegration/aggregation behaviour may be important for kinetics of the processes and possibly influencing the biological activity. The colloidal dynamics (and for Ag NP the dissociation) and their impact on uptake (TP3) and toxicity (TP2) will be investigated in aqueous solution at conditions relevant for different exposure media. The description of particle morphology will include shapes and sizes of nanoparticles obtained from electron microscopy and dynamic light scattering techniques.