This chapter provides a relatively non-technical introduction to complex systems, from a scientific perspective, at a level useful to both scientists and narrative theorists. It covers several complexity science concepts: it discusses models and meta-models, and how these can be used to define the concepts of novelty, innovation, and emergence; it distinguishes the concepts of non-linearity of scale, and non-linearity in time; it introduces several concepts from dynamical systems theory, including trajectories through state space, deterministic behaviour, attractors, bifurcations, and the idea of "edge of chaos". It discusses how these concepts are used in their own domains, and how they might be applied metaphorically.