We highlight a number of examples of complex thinking from ancient times to the current edge. We refer the earlier complexity perspectives to the cutting-edge understanding of complex adaptive (economic) systems. This illustrates that simplistic (neoclassical) equilibrium thinking is a big exemption rather than the 'normal' in HET. Since the 1980s, the mathematical, statistical, data, and computational resources have been fully developed and in fact successfully combined to finally demonstrate that complexity economics is the way of doing realistic and scientific economics, in contrast to reductionist and simplistic equilibrium modelling. We illustrate the potential of such scientific real-world economics with an example from evolutionary-institutional economics, and we consider modern policy implications of such complex economic thinking.