a, Amount of dimerization events occurring for the basal wild-type µOR. The linear fit (magenta) shows the expression range up to which strict single molecule analysis can be conducted without bias due to overlapping of PSFs. b, Representative image of simulated movies comprising the same distribution of diffusion classes and diffusion- coefficients as real movies. Particles undergoing confined and directed diffusion were modelled using different potential fields as described in the methods section. [Data in (a) is fitted from n = 20 cells imaged in three independent experiments. Numbers and statistics on the simulations are provided in methods section.].