High entropy alloys add a new dimension, atomic-scale randomness and the associated scale-dependent composition fluctuations, to the traditional metallurgical axes of time-temperature-composition-microstructure. Alloy performance is controlled by the energies and motion of defects (dislocations, grain boundaries, vacancies, cracks, ...). Randomness at the atomic scale can introduce new length and energy scales that can control defect behavior, and hence control alloy properties. The axis of atomic-scale randomness combined with the huge compositional space in multicomponent alloys thus enables, in tandem with still-valid traditional principles, a new broader alloy design strategy that may help achieve the multi-performance requirements of many engineering applications. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.