Hartland (professor emeritus, interfacial phenomena, ETH Swiss Federal Institute of Technology, Switzerland) presents contributions offering an understanding of the physical phenomena and mechanisms at work in surface and interfacial tensions and gradients, their direct impact on interface shape and movement, and their significance to numerous applications. The measurement of tension and contact angles, interface shapes, bubble motion and nucleation, the effect of surfactants, foam formation and stability, and fiber wetting are some areas examined. Emphasis is on physical understanding backed by experimentation and theoretical interpretation. Material will be of interest to scientists and engineers concerned with problems involving surface effects associated with surface tension, contact angles, and wetting.