Many simple nonlinear deterministic systems can behave in an apparently unpredictable and chaotic manner. This realisation has broad implications for many fields of science. Some basic concepts and properties in the field of chaotic dynamics of dissipative systems will be reviewed in this talk, including strange nonchaotic attractors, chaos-induced intermittency, and fractal basin boundaries. I will use some of these properties in application topics, including the control of chaos in the brain. I will then go a step further by arguing that a complex system is made up of many states that are interrelated in a complicated manner. The ability of a complex system to access those different states, combined with its sensitivity, offers great flexibility in manipulating the system’s dynamics to select a desired behaviour.