This lecture explores the form and function of complex systems, focusing on the workshop's theme of transport, metabolism, and design in Nature and Society. Working hypotheses include the coevolution of 'mass' and 'transport networks' leading to metabolism/scaling observed in different systems. The lecture discusses how branching morphogenesis can be seen as an optimal transport problem and how a unifying theory of form/function can aid in designing urban infrastructures and medical technologies. The Blue Brain Project's goal of digitally reconstructing and simulating the mouse brain is also highlighted.