“Von Uexküll was interested in how living beings subjectively perceive their environment. Picture, for example, a meadow as seen through the compound eyes of a fly, and then again as seen in black and white by a dog, and heard in a wider range of sounds. Von Uexküll called these subjective worlds Umwelt.” from Jakob_von_Uexküll

http://www.math.uni-hamburg.de/math/ign/hh/biogr/uexkuell.htm