Methods and Phenomena, 4: Their Applications in Science and Technology: Microweighing in Vacuum and Controlled Environments focuses on the principles, methodologies, and approaches involved in micro mass measurements. The selection first elaborates on introduction and microbalance review, beam microbalance design, construction and operation, and sources of error in microweighing in controlled environments. Discussions focus on Brownian motion, Knudsen forces, gravitational forces, microbalance construction and operation, auxiliary equipment for operation of a vacuum microbalance, undesirable disturbances or forces, calibration techniques, and classification of various types of microbalances. The text then takes a look at physical adsorption studies and chemisorption studies with the vacuum microbalance, simultaneous microgravimetric and residual gas analyzer measurements, and simultaneous measurement of mass change and infrared spectra. Topics include chemisorption results obtained on other solids and silver powders, probing the surface phase, quantitative information from adsorption and desorption, measuring techniques, and examples of physisorption measurements and their evaluation. The manuscript examines unusual applications of the vacuum microbalance and high temperature reaction studies, as well as empirical and theoretical rate laws, permeation of water vapor through plastic membranes, and measurement of permittivity and dielectric loss factor. The selection is a valuable source of data for researchers wanting to explore microweighing in vacuum and controlled environments.