Florian Mildenberger from Europa University Frankfurt/Oder and Bernd Herrmann from the University of Göttingen comment on Jakob Johann von Uexküll's work "Environment and Inner World of Animals" from today's perspective. This book marks the discovery of "environment" in the life sciences, has accelerated the development of ecology and ethology, and, with its central concept of "environment," is the root of the Green movement as well as a key publication in environmental history. After a brief introduction to the question of who Uexküll was and how he was perceived during his lifetime, his biography and work are presented. Subsequently, central points of the work and contemporary criticism of it are discussed. The focus is on the functional circle, the theory of environment, the restriction to animals, and the philosophical connections to Kant. Finally, the authors further explore the topic.