  When two objects at different temperatures are separated by a vacuum gap they
can exchange heat by radiation only. At large separation distances (far-field
regime) the amount of transferred heat flux is limited by Stefan-Boltzmann's
law (blackbody limit). In contrast, at subwavelength distances (near-field
regime) this limit can be exceeded by orders of magnitude thanks to the
contributions of evanescent waves. This article reviews the recent progress on
the passive and active control of near-field radiative heat exchange in two-
and many-body systems.
