The occurrence of flow configuration (pattern, shape, structure) is a universal phenomenon. From atmospheric circulation to living cells, the occurrence of flow configuration is associated to the very existence of these systems. Why is configuration a characteristic of natural flow systems? Is there a physical law from which rhythms (flows) and patterns (configurations) can be deduced? It is shown here that the occurrence of flow configuration can be both explained and predicted on the basis of a single law - the constructal law. This law states that for a flow system to persist in time it must evolve in such way that it provides easier access to its currents. Coral colonies and pedestrian crowd dynamics occur in very different physical environments and form dissimilar patterns. The flow configuration phenomena at work in either of these systems are, however, one and the same and can be explained by the constructal law. Within the same framework, strategies for optimization of pedestrian flows in a real-world environment are also presented.