Our local interstellar medium has been unveiled to have rich and diverse chemistry, which includes the presence of complex organic molecules. When compared with carbon and oxygen chemistry, not much is known about nitrogen chemistry; especially regarding its origin and how chemical complexity builds up across different evolutionary stages during the process of star formation. One way to gain more insights into the matter is by exploring the level of diversity and complexity of nitrogen-bearing molecules at the early stage of star formation. In the poster, we present our recent census of nitrogen-bearing molecules, including some of the first detection in the interstellar medium, towards a quiescent molecular cloud, named G+0.693-0.027, with high sensitivity unbiased spectral surveys obtained by IRAM 30m and Yebes 40m telescope. This molecular cloud represents one of the most chemically rich sources in our Galaxy and it has been suggested to be on the verge of star formation, which allows us to study the interstellar nitrogen chemistry at a very early evolutionary stage of star formation. We report the detection of nitrogen-bearing molecules in terms of their derived excitation conditions and molecular abundances. These results are compared with various astronomical sources including starless and pre-stellar cores, shocked regions, low-mass and high-mass star-forming regions. Latest results from chemical modelling and predictions from theoretical calculation are also discussed to provide constraints on the formation pathway(s) of the detected molecules.