  The ability to spatially and temporally map nanoscale environments in situ
over extended timescales would be transformative for biology, biomedicine, and
bioengineering. All nanometer objects, from nanoparticles down to single
proteins, scatter light. Interferometric scattering stands as a powerful tool,
offering ultrasensitivity and resolution vital for visualizing nanoscale
entities. Interferometric scattering from an individual nanoparticle down to an
individual protein has been detected; however, resolving adjacent nanometer
objects with interferometric scattering has not yet been demonstrated. In this
work, we present interferometric phase intensity nanoscopy to resolve adjacent
nanometer objects with interferometric scattering. We demonstrate that
multiphase and sensitivity of interferometric phase intensity nanoscopy reveals
ellipse Airy patterns correlated with nanostructural features. We show that
eliminating background fluctuation by employing circular polarized illumination
in interferometric phase intensity nanoscopy is essential to separate proximal
nanometer objects below the diffraction limit. We envision interferometric
phase intensity nanoscopy for resolving a variety of adjacent nanometer objects
from nanoparticles down to proximal proteins in situ over extended time periods
for wide range of applications in biology, biomedicine and bioengineering.
