Using evolution as a guiding principle, researchers have successfully engineered bacteria-yeast hybrids to perform photosynthetic carbon assimilation, generate cellular energy and support yeast growth without traditional carbon feedstocks like glucose or glycerol. By engineering photosynthetic cyanobacteria to live symbiotically inside yeast cells, the bacteria-yeast hybrids can produce important hydrocarbons, paving new biotechnical pathways to non-petroleum-based energy, other synthetic biology applications, and the experimental study of evolution.