  Energy transport theories are being revisited at the nanoscale, as
macroscopic laws known since a century are broken at dimensions smaller than
those associated with energy carriers. For thermal radiation, where the typical
dimension is provided by Wien's wavelength, Planck's law and associated
concepts describing surface-to-surface radiative transfer have to be replaced
by a full electromagnetic framework capturing near-field radiative heat
transfer (photon tunnelling between close bodies), interference effects and
sub-wavelength thermal emission (emitting body of small size). It is only
during the last decade that nanotechnology has allowed for many experimental
verifications-with a recent boom-of the large increase of radiative heat
transfer at nanoscale. In this minireview, we highlight the parameter space
that has been investigated until now, showing that it is limited in terms of
inter-body distance, temperature and object size, and provide clues about
possible thermal-energy harvesting, sensing and management applications. We
also provide an outlook on open topics, underlining some difficulties in
applying single-wavelength approaches to broadband thermal emitters while
acknowledging the promises of thermal nanophotonics and observing that
molecular/chemical viewpoints have been hardly addressed. Context: revisiting
thermal radiative energy transport and conversion at the nanoscale
