New technologies for producing energy crops and trees based on fundamental studies have been developed to improve self-sufficiency in food and feed supplies in addition to achieving sustainable natural resources. Energy crops and trees with improved leaf growth, light interception of crop canopy, photosynthetic rate, lodging resistance, and saccharification efficiency of lignocellulose, among many other traits, need to be explored. DNA marker-assisted selection using genome information has been developed as a powerful tool for breeding new bioenergy crops and trees. In this chapter, the concept and basic technologies for producing biomass from herbaceous energy crops and trees, ecophysiological characteristics for high yield and biomass production, genetic analyses of the traits responsible for biomass production, and molecular breeding for improving these traits are discussed. The definitions of herbaceous energy crops for the first and second generations, agronomy and breeding technology for these crops are explained. Recent studies on woody cell wall formation and genetic improvements associated with biomass saccharification in energy crops and woods are introduced. © 2014 Elsevier Inc. All rights reserved.