A) Single, 290nm-diameter fluorescent bead encapsulated within a hemispherical, water droplet (∼20μm diameter). B) Particle tracking (gray lines) showed the diffusion path of the bead inside the droplet over 200 frames. For each displacement, the displacement corresponding to Δx (C) and Δy (D) were recorded, binned into histograms, and fit with equation 3 to determine the diffusion coefficient in each dimension. In this example, integration time for the camera was 100 msec, frame rate was 155 msec, and 800 images were acquired.