Molecular motors, an important class of molecular machines, harness various energy sources to generate unidirectional mechanical motion. The operational principles of molecular motors are distinct from those of man-made macroscopic motors, because they have nanoscale dimensions and generally work in a solution environment where viscosity is dominant. Under these low Reynolds number, overdamped conditions, they cannot rely on inertia to sustain motion. Furthermore, they are continually agitated by random Brownian motion, which provides both challenges and opportunities for energy conversion mechanisms. To understand the mechanisms how molecular motors made of proteins can work so well under these unique conditions, Professor Iino’s Lab has been developing single-molecule imaging techniques which enable visualization of dynamic motions of protein molecular motors with microsecond time resolution and angstrom localization precision. In this colloquium, he will first introduce their techniques and then discuss universality and diversity in the mechanisms of protein molecular motors.