Many things around us can be described as networks: The web of friendships across the planet, the Internet, chains of historical events, you name it. These networks contain information about the forces that formed it. This information -- the network structure -- tells us not only how the network has formed, but more also how dynamical systems (disease spreading, information flow, vehicular traffic, etc.) behaves. In biology and society there are often also large numbers of entities that makes up a whole whose appearance can be hard to predict from the entities' behavior. Modeling of such behavior has a long tradition in statistical physics. This is not to say that statistical physics can be immediately applied to biology and sociology -- the different traits of the entities may be more significant than their similarity. Epidemics is a great concern for many people. To be able to fight the spread of diseases we must understand how people make the contacts that spread diseases. With that knowledge we can say how to inhibit epidemics by vaccination or awareness campaigns etc.

Within a decade Internet grew from an academic obscurity to an infrastructure of everyday use. The Internet protocols, originally developed for much smaller networks, now became hard-to-replace standards. At the same time the Internet fits all descriptions of a complex systems. It also produces very accurate data. Thus complex system theories are very apt and useful for creating the protocols of the future. When many similar entities interact their behavior may be fundamentally different from what can be anticipated from the individual particles. One example is when liquid freezes -- the atoms just moves more and more slowly, but at a certain point the liquid has turned into a solid. There are a multitude of systems with phase transitions, luckily one can group the transitions into "universality classes" of transitions with the same characteristics. Ecology is one of the oldest sciences to study emergent properties of interacting agents. Population biology studies the interaction of animals and plants and self-organizing aspects of such systems are interesting to me. Furthermore I believe these fields are among the most important in the world of today.