From the molecular to the organismic level, animal and plant vascular networks are extraordinarily complex and can exhibit intricate architectures and rich dynamics. It still remains unknown what determines the morphology and function of the networks. In this talk we present solutions of a phenomenological developmental model that we show is applicable to both plant leaf and animal venation. The model captures the positive feedback loop between flow and vein conductivity and predicts a rich spectrum of vascular phenotypes. We demonstrate that the network topologies generated by this simple feedback loop represent a trade-off between optimizing power dissipation, construction cost, and damage robustness. We identify the Pareto-efficient front and eventually the spectrum of venation phenotypes that evolution is expected to favor and select.