Quantum gravity can be classified into Nuclear quantum gravity (NQG), Cosmic quantum gravity (CQG) and Unified quantum gravity (UQG). In the context of NQG, by assigning four gravitational constants to the observed four interactions- ‘string theory’ can be made practical to accommodate the three atomic interactions, ‘$\hbar$’ can be understood as an outcome of electroweak gravity and nuclear gravity concepts can be implemented in basic nuclear physics in a full-fledged manner. In the context of CQG, considering the concept of ‘light speed growth of a Planck scale black hole’ and scaling the famous Hawking’s black hole temperature formula- issues like big bang, temperature, redshift, flatness, acceleration and dark energy can be reviewed at fundamental level. Dark matter can be understood as a representation of ‘super gravity’ associated with galactic (visible and missing) baryonic mass greater than $4 \times 10^{38}$ kg (200 million solar masses). Studying the concepts of NQG and CQG, in a systematic approach, basics of UQG can be established.