How biology creates networks that are cheap, robust, and efficient

From veins that deliver oxygen to tissues to xylem that send water into stems and leaves, vascular networks are a crucial component of life. In biology, there is a wide range of unique patterns, like the individualized structures found on leaves, along with many conserved structures, such as named arteries and veins in the human body. These two observations led scientists to think that vascular networks evolved from a common design, but how, exactly, could nature create so many complex structure...