  Video-rate super-resolution imaging through biological tissue can visualize
and track biomolecule interplays and transportations inside cellular organisms.
Structured illumination microscopy allows for wide-field super resolution
observation of biological samples but is limited by the strong absorption and
scattering of light by biological tissues, which degrades its imaging
resolution. Here we report a photon upconversion scheme using lanthanide-doped
nanoparticles for wide-field super-resolution imaging through the biological
transparent window, featured by near-infrared and low-irradiance nonlinear
structured illumination. We demonstrate that the 976 nm excitation and 800 nm
up-converted emission can mitigate the aberration. We found that the nonlinear
response of upconversion emissions from single nanoparticles can effectively
generate the required high spatial frequency components in Fourier domain.
These strategies lead to a new modality in microscopy with a resolution of 130
nm, 1/7th of the excitation wavelength, and a frame rate of 1 fps.
