Prof. Art Krener was honored with the Institute for Electrical and Electronics Engineers (IEEE) Control Systems Award, Dec. 13. The prestigious award recognizes outstanding contributions to control systems engineering, science or technology. Throughout a long and distinguished career, Dr. Krener has made seminal and myriad contributions to the development of methods for the control and estimation of nonlinear dynamical systems and stochastic processes. Modern linear control and estimation theory can trace its beginnings back to several key developments around 1960. One of them was the definition, by Kalman, of the basic concepts of linear control theory. However, Kalman’s work did not produce a similar theory for nonlinear systems. Working with Robert Hermann, Dr. Krener conducted seminal research in nonlinear systems, resulting in a 1977 paper that provided the definitive treatment of controllability and observability for nonlinear systems. It is difficult to overstate the importance of this 1977 paper. Dr. Krener’s work would go on to be selected by the IEEE Control Systems Society as one of the Twenty-Five Seminal Papers in Control published across the entirety of the twentieth century. The remarkable progress and evolution in the development of nonlinear systems theory that has occurred in the decades since Dr. Krener’s original publication would not have been possible without his foundational work. The impact of an innovator can be measured not by how they effect change in one field, but across multiple fields of endeavor. By this measure, Dr. Krener’s impact has been almost without equal. While he is known for the depth of his insights, Dr. Krener’s efforts are remarkably broad, and span nonlinear representation theory, observer design, feedback linearization, control of bifurcations, optimal/bang-bang control, nonlinear H-infinity control, solutions to Hamilton-Jacobi PDEs, and the estimation and analysis of stochastic systems. When we speak of “giants” in our profession, we speak of individuals like Dr. Krener.