Johannes Nicolaus Brønsted was a Danish chemist born on February 22, 1879, and he is best known for his contributions to acid-base theory. Along with Thomas Martin Lowry, he developed the Brønsted-Lowry theory in 1923, which defines acids as proton donors and bases as proton acceptors. This theory expanded the understanding of acid-base reactions beyond the limitations of the earlier Arrhenius theory. Brønsted's work significantly influenced the field of chemistry, particularly in understanding chemical reactions in various environments, including biological systems. He also contributed to the study of catalysis and reaction kinetics, making him a prominent figure in physical chemistry. Brønsted passed away on December 16, 1947.