In this webinar, previously given at a Royal Society of Chemistry (RSC) and the National Physical Laboratory (NPL) symposium in the UK, Dr. Jan "Kuba" Tatarkiewicz will discuss the influence of various experimental parameters determined by different methods to measure the concentration of particles in colloids, especially in poly-dispersed and poly-material samples. Dr. Tatarkiewicz will compare principles of measurements for established technologies such as transmission electron microscopy (TEM), flow cytometry (FC), resistive pulse sensing (Coulter), nanoparticle tracking analysis (NTA) as well as improvements introduced to the latter by multispectral advanced nanoparticle tracking analysis (MANTA). Dr. Tatarkiewicz will present experimental results obtained for standardized samples and colloids encountered in research studies in diverse fields of interest. Details of calibrating instruments that use MANTA will also be discussed.