False-colour transmission electron micrograph of a plasmid of bacterial DNA. A plasmid is a molecule of DNA that can exist apart from the chromosome in a bacterium, & which can replicate on its own. This plasmid, designated pSC101, was the carrier molecule in the first genetic engineering experim- ents, carried out at Stanford University by S. Cohen & H. Boyer. Foreign DNA was spliced to it & the composite or chimeric" plasmid was then intr- oduced into an Escherichia coli bacterium, where it propagated & expressed the genetic information carried by the transplanted DNA. These experiments made possible the biotechnology revolution. Magn- ification: x30,000 at 35mm, x60,000 at 6x7cm size."