This chapter turns to genetic intensification, which consists of developing crop and livestock crosses that contain genes capable of producing improved yields on a sustainable basis. These crosses often show increased vigor, such that they tend to outperform both parents, although for reasons that are not fully clear. Today, hybrids and crosses are the basis for most improved crop and livestock breeds, including wheat, rice, maize, and dairy cattle. Nevertheless, as has been long recognized, conventional breeding techniques have practical limitations. The application of modern cellular and molecular biology is pursued through four practical techniques: marker-assisted selection, cell and tissue culture, recombinant DNA, and gene editing. The chapter examines the extent to which these interventions contribute to sustainable intensification: improving nutrition, increasing resilience to pests, diseases, and climate change, and improving nitrogen fixation.