Although the notion of systemic risk gained prominence with respect to financial systems,it is a generic term that refers to risks of increasing importance in many domains-risks that cannot be tackled by conventional techniques of risk management and goveance.We build on a domain-overarching definition of systemic risks by highlighting crucial properties that distinguish them from conventional risks and plain disasters.References to typical examples from various domains are included.Common features of systemic risks in different domains-such as the role of agents and emergence phenomena,tipping and cascading,parameters indicating instability,and historicity-tu out to be more than noncommittal empirical observations.Rather these features can be related to fundamental theory for relatively simple and well-understood systems in physics and chemistry.A crucial mechanism is the breakdown of macroscopic pattes of whole systems due to feedback reinforcing actions of agents on the microlevel,where the reinforcement is triggered by boundary conditions moving beyond critical tipping points.Throughout the whole article,emphasis is placed on the role of complexity science as a basis for unifying the phenomena of systemic risks in widely different domains.