Nanoparticle Tracking Analysis in 2D: Camera-Plane Brownian Motion

Extracellular vesicles like exosomes are too small to resolve individually under a light microscope, yet labs size and count them every day using nanoparticle tracking analysis (NTA): a laser sheet lights up each particle as a point of scattered light, a camera follows its Brownian wandering frame by frame, and the Stokes-Einstein relation converts how far it drifted into how big it is. This 2D companion to the 3D NTA simulator keeps the same real Stokes-Einstein physics but computes it independently for the view a real NTA camera actually captures: a 2D projection of 3D Brownian motion onto the imaging plane, whose mean-square displacement grows as 4·D·t rather than the 3D relation's 6·D·t — a distinction confirmed here numerically, not assumed. Drag to pan and scroll to zoom the field of view while a population of vesicles diffuses with a diffusion coefficient set by their own diameter, sample temperature, and medium viscosity; a live MSD-vs-time strip and a size-distribution histogram, both genuinely 2D-native diagnostics, show the tracking measurement converge on the population you set up and its MISEV-style exosome/microvesicle/apoptotic-body classification.