Against this background, any attempt at defining systems biology might seem futile and potentially harmful. However, anyone who is labeling oneself as a systems biologist will have noticed that the question “What is Systems Biology?” comes up in conversation with one's fellow scientists with an astonishing regularity. Usually, the question is followed by a personal definition of the field, along the lines of “to me, all biology is systems biology” or “it's just one of those hypes that you need to follow to get grant money”, or, in the most positive cases “this holistic approach is the future of biology, we all will have to do it”. Faced with this challenge, systems biologists have repeatedly tried to come up with more descriptive definitions of what they are doing. These attempts range from brief sound bites, such as “a new kind of biology” or “the successor of molecular biology” to comprehensive, detailed examinations of the historical foundations of the field and its philosophical underpinnings