  Quantitative phase microscopies (QPMs) have been mainly used for applications
in cell biology, for around 2 decades. In this article, we show how
cross-grating phase microscopy (CGM), a high-resolution, high-sensitivity QPM,
recently expanded the scope of QPMs to applications in nanophotonics. In
particular, this article explains how the intensity and phase images acquired
by CGM can be processed to determine all the optical properties of imaged
nanoparticles, 2D-materials and metasurfaces. We also explain how CGM can be
used as a temperature microscopy technique. This latter imaging modality led to
a large variety of works in the 2010s based on the optical heating of plasmonic
nanoparticles for photothermal studies in physics, chemistry and biology at the
microscale, in which label-free, microscale temperature measurements were
pivotal.
