'Hubble volume’ can be considered as a key tool in cosmology and microscopic physics. Note that at any given cosmic time, the product of ‘cosmic critical density’ and ‘Hubble volume’ gives a characteristic 'cosmic mass' and can be called as the ‘Hubble mass’. Schwarzschild radius of the ‘Hubble mass’ again matches with the ‘Hubble length’. The authors emphasize the fact that this coincidence is having deep connection with the cosmic geometry and the cosmological and microscopic physical phenomena. At any given cosmic time, ‘Hubble length’ can be considered as the gravitational or electromagnetic interaction range. In a unified approach observed cosmic red shift can be re-interpreted as an index of cosmological galactic atomic light emission phenomenon. In a unified approach and by increasing the number of applications of Hubble mass and Hubble volume in microscopic physics, concepts of ‘Black Hole Cosmology’ can be well confirmed. Clearly speaking, compared to the Big bang model, advantage of Black hole cosmology lies in confirming its validity through the atomic and nuclear experimental results. In this model, forever rotating at light speed, high temperature and high angular velocity small sized primordial cosmic black hole of mass $\sqrt{\frac{e^2}{4 \pi \epsilon_0 G}}$ gradually transforms into a low temperature and low angular velocity large sized massive primordial cosmic black hole. At any time $\H_t$ represents the angular velocity. At its ending stage of expansion, for the whole cosmic black hole as $\H_t$ practically remains constant, its corresponding thermal energy density will be ‘the same’ throughout its volume. This ‘sameness’ may be the reason for the observed ‘isotropic’ nature of the current CMB radiation.