Fig. 2

Resolving two UCNPs at sub-diffraction distance via uSEE microscopy. a Imaging at diffraction-limited resolution does not differentiate the two UCNPs, separated by 206 nm. b uSEE microscopy resolves the two UCNPs. The line scans are obtained through a cross section indicated by the gray arrows. The dashed black box indicates the span of the experimentally measured area. The area outside of the black box contains a flat background equal to the average background in the measured area. This facilitates the visual comparison of panels (a, b)