Historically, the deviation from Ideal Gas law in the case of real gases was the first realization of intermolecular interactive forces. These are weak van der Waal’s forces (or London forces) that exist in all atomic and molecules gases. Later, in 1937 Linus Pauling introduced another type of interaction, namely, hydrogen bonding interaction based on the empirical observations available by then. In the last several decades a number of different types of weak interactions and their influence on dictating the properties of substances, influences on the activities have been reported. Our group has been working on experimental characterization of hydrogen bonding interaction prevalent in biological milieu. In this talk I will focus mainly on our work on unconventional hydrogen bonding interactions involving sulfur and carbon atoms.