Hypothetical design space example valid for both engineering and biology illustrating the optimisation of two parameters x1 and x2 of a construction. The parameters can be of a different kind, including length measurements, material properties, optical properties, etc. The third, vertical axis shows a measurable performance. The two parameters x1 and x2 can be changed, with each combination resulting in a different performance value (red dots). With two parameter dimensions, a surface results from different parameter settings that can be depicted as a ‘landscape’. Optimisation is the process indicated by the arrows. By changing the parameters, an ever better performance can be achieved, leading to an optimum at the top of a ‘hill’.