This paper aims to give an insight into developments that contributed to the significance of the work of Jakob von Uexküll and stresses the importance of his occupation in Hamburg. A biographical survey pays tribute to the implication of the historical pretext and context. A scientific survey describes findings and ideas of Uexküll that proved important for the development of biology and the cognitive sciences. In addition, this paper sets out to reject the common notion that Uexküll’s concepts were ideas (...) of a purely theoretical and philosophical character. It confirms that in fact the central aims of his work were to sustain the empirical method in biology and to give biology a sound epistemological basis. Some examples show how historical and theoretical developments converged at Uexküll’s Institut für Umweltforschung in Hamburg and ignited a productive research activity. (shrink)