Man's quest for time started in the very beginning of civilization, partly because of necessity and partly because of curiosity. Similarly, man's exploration of length or distance scales also started early, in the process of making machines, paintings and abodes. We need both the scales to understand nature, both near and far, fast and slow. Our newly developed ability to probe, observe and understand the behaviour of atoms and molecules has revolutionized our understanding of the natural world and has led to many important scientific and technological advancements. At the molecular scale, physical, chemical, and biological processes are governed by fundamental principles of thermodynamics, statistical mechanics, quantum mechanics, and molecular dynamics. These principles allow researchers to predict the behaviour of molecules under a variety of conditions and to develop strategies for manipulating their properties. In this talk we shall explore how time and length scales have been used to understand fundamental processes, taking examples primarily from chemistry and biology.