With the increasing demand in energy use, new energy harvesting methods and prominent technologies have received significant attention. In this regard, near-field radiation is a newly developed efficient heat transfer mechanism to enhance heat transfer in various energy technologies. Much effort has been devoted to understanding the underlying mechanism of near-field radiation. The existing studies in literature extensively describe theories behind the near-field radiative transfer between two surfaces. In this work, we investigate in details contributing factor to the near field radiative transfer, including surface-phonon polaritons and evanescent waves, thus providing a comprehensive description of the near-field radiative transfer. Limited experimental studies have been put forth so far, however a sufficiently accurate experiment confirming the theory still needs to be developed to determine radiative heat transfer between two flat plates. Experiments are underway to validate the theoretical predictions.