The reaction of reducing carbohydrates with amino compounds described in 1912 by Louis-Camille Maillard is responsible for the aroma, taste, and appearance of thermally processed food. The discovery that non-enzymatic conversions also occur in organisms led to intensive investigation of the pathophysiological significance of the Maillard reaction in diabetes and ageing processes. Dietary Maillard products are discussed as "glycotoxins" and thus as a nutritional risk, but also increasingly with regard to positive effects in the human body. In this Review we give an overview of the most important discoveries in Maillard research since it was first described and show that the complex reaction, even after over one hundred years, has lost none of its interdisciplinary actuality. Food for thought: The reaction of reducing carbohydrates with amino compounds described by Louis-Camille Maillard in 1912 is responsible for the aroma, taste, and appearance of thermally processed food. Corresponding reactions occur in the body and are important in diabetes and ageing processes. A historical overview of the most important findings is given in this Review.