The sun is the principle source of energy for our planet, and photosynthesis is the primary mechanism by which that energy is captured and stored in the form of reduced carbon. An outcome of these biochemical events is that plants represent a quantitatively important, sustainable, and carbon-neutral source of energy for humans. In order to maximize the utility of plants for this purpose, it is important that we gain control of the processes associated with energy capture and storage, including the molecular mechanisms that allocate fixed carbon to the myriad biochemical pathways in plants. One of the most significant of these is the phenylpropanoid biosynthetic pathway which leads to the deposition of lignin. Lignin is a cross-linked phenolic polymer that makes the cell walls of specialized plant cells more rigid. Its synthesis represents the single largest metabolic sink for phenylalanine in the biosphere and as such represents a huge metabolic commitment for plant metabolism. Lignin is also a significant barrier to the use of crops for livestock feed, pulp and paper production, and to the generation of cellulosic biofuels. Our objective is to push forward our basic understanding of lignin biosynthesis while simultaneously adding to our ability to engineer plant metabolism so that it can be modified for the improvement of agriculture.