Plastids are interesting targets for metabolic engineering using the tools of synthetic biology. Plastids carry their own genome, which can be manipulated genetically in many algae and plants. Incorporating foreign genes into the plastid genome offers valuable benefits, such as high-level foreign protein expression and the absence of gene silencing. Here, we review progress in bioengineering of chloroplasts to produce valuable metabolites and proteins. Various strategies for enhancing yields of desired products, including design of operons, fusion proteins for improved translational efficiency, protein scaffolding, metabolic channeling and storage, are described. Efforts to control plastid differentiation also offer promising ways of turning plastids into controllable bio-factories, and the construction of synthetic plastids optimized for specific functions would be a major advance.