Since plastids are not transmitted to pollen, expressing transgenes in chloroplast genomes (transplastomics) is viewed as a way of preventing the transgenes' spread to weedy relatives. Now on page 333, Staub et al. show that human somatotropin, a therapeutic protein used to treat disorders such as hypopituitary dwarfism and HIV wasting syndrome, can be produced at high levels and in an active form in tobacco chloroplasts. Given that there are no known plastid-encoded proteins that contain disulfide bonds, it was particularly encouraging that the recombinant somatotropin was appropriately disulfide bonded.