My stays in Bristol, U.K., and Clarkson University, Potsdam, N.Y., USA, were essential for my continuation in the field of nanoparticles production and characterization. Professor Ottewill in Bristol was very well known for his research on the synthesis of polystyrene spheres, their stability and electrokinetic characterization. In Clarkson University Egon Matijevic produced a great variety of inorganic nanoparticles using original methods, which have been reproduced for many years. I will always be indebted to both of them for giving a solid basis to my starting work.