  The emission of thermal radiation is a physical process of fundamental and
technological interest. From different approaches, thermal radiation can be
regarded either as one of the basic mechanisms of heat transfer, as a
fundamental quantum phenomenon of photon production, or as the propagation of
electromagnetic waves. However, unlike light emanating from conventional
photonic sources, such as lasers or antennas, thermal radiation is
characterized for being broadband, omnidirectional, and unpolarized. Due to
these features, ultimately tied to its inherently incoherent nature, taming the
thermal radiation constitutes a challenging issue. Latest advances in the field
of nanophotonics have led to a whole set of artificial platforms, ranging from
spatially structured materials, and much more recently, time-modulated media,
offering promising avenues for enhancing the control and manipulation of
electromagnetic waves, from far to near-field regimes. Given the ongoing
parallelism between the fields of nanophotonics and thermal emission, these
recent developments have been harnessed to deal with radiative thermal
processes, thereby conforming the current basis of thermal emission
engineering. In this review, we survey some of the main breakthroughs carried
out in this burgeoning research field, from fundamental aspects, theoretical
limits, the emergence of new phenomena, practical applications, challenges, and
future prospects.
