This chapter traces the story from early atomic theories to the cutting-edge field of single-molecule probing and its impact on drug discovery. Traditional ensemble methods, which averaged the behavior of countless molecules, have given way to techniques capable of observing biomolecular interactions one molecule at a time. These high-resolution methods reveal dynamic processes such as protein folding, ligand binding, and conformational changes with unprecedented clarity, giving critical insights for developing more targeted and effective therapeutics. The convergence of single-molecule analysis with artificial intelligence has further accelerated drug discovery, enabling screening informed by rich and massive experimental data. The second part of the chapter chronicles the historic and technical breakthroughs that led to super-resolution microscopy and single-molecule localization techniques. These innovations not only transformed imaging but reshaped our fundamental understanding of cellular processes in health and disease. As a prelude to the coming chapters on biophotonics, this narrative highlights the power of optical tools in revealing life at its most fundamental scale, and the bold thinking that drives such scientific revolutions.