Multiple societal benefits underlie U.S. Department of Energy (DOE) research efforts to support a viable and sustainable domestic biofuel and bioproducts industry from nonfood lignocellulosic plant biomass. These benefits include ensuring future energy security, lowering greenhouse gases to mitigate climate impacts, diversifying the range of available biobased products, producing fewer toxic chemicals and byproducts, creating jobs in rural areas, and improving the trade balance. Cellulose?the most abundant biological material on Earth?is contained within plant cell walls in the form of long, tightly bound chains of sugars (polysaccharides) that can be converted into biofuels and bioproducts by microbes. Physically accessing these sugars, however, is difficult because the cellulose is embedded within a matrix of other polymers including hemicellulose and lignin, making it resistant to degradation. This resistance, called recalcitrance, along with a lack of efficient methods to convert lignocellulose to useful products are major impediments to the cost-effective production of biofuels and bioproducts from plant biomass. Innovation stemming from advanced biotechnology-based research is key to accelerating needed improvements in the sustainable production of lignocellulosic biomass, its deconstruction into sugars and lignin, and conversion.