HanswalterGiesekus in 2022, this special collection explores his personal life, scientific accomplishments, and contemporary studies that draw on his contributions.Hanswalter Giesekus was born on January 4, 1922, in H€ uckeswagen, a small town in North Rhine-Westphalia, Germany. His early life was marked by the hardships of the Great Depression and the rise of National Socialism in Germany. He began studying physics at the University of G€ ottingen in 1940, but his studies were interrupted by World War II and his compulsory military service. After the war, in 1945, he was able to resume his studies because he had not been involved in National Socialist activities, and he completed them in 1948. He obtained his doctorate in 1950 and then joined the chemical engineering company Bayer A.G., where he was introduced to rheology by his colleague Dr. Juri Pawlowski. This sparked an interest in Hanswalter, turning rheology into a passion. He pursued rheology more as a hobby until he was appointed Professor of Fluid Mechanics at the Technical University of Dortmund in 1970. Hanswalter made significant contributions to both theoretical and experimental rheology, making him one of the foundational rheologists. One of his major contributions, the Giesekus model, is a constitutive equation for polymer solutions and melts. This equation is still widely used today because it can predict nonzero second normal stress difference, stress overshoot at the onset of simple shear flow, and finite extensional viscosity. His remarkable scientific achievements earned him the Bingham Medal from the Society of Rheology in 1976 and the Weissenberg Prize from the European Society of Rheology in 1996. He also served as Editor-in-Chief of Rheologica Acta from 1975 to 1987. Hanswalter retired in 1986 and passed away in Dortmund, Germany, on December 4, 2017, at the age of 95. He was married to Hanna Hoppe for 59 years, and they had six children.Below is a brief overview of the contents of this special collection, beginning with personal notes from his former close colleagues and