The genetic code is dynamic it, or its readout, can be specifically changed by mRNA signals that modify the behavior of on-board ribosomes. Many viruses use recoding to maximize utilization of information in small genomes, and probably all organisms use recoding in at least some genes for expanding the regulatory repertoire. The volume will detail specific recoding examples to understand the mechanisms and the mRNA signals. It will continue to detail the biochemical and genetic approaches to identify and study the cellular factors involved in recoding. The signals in mRNA that dictate recoding often include complex folded structures of the RNA, which we are studying by a combination of microbiology, genetics, biochemical and NMR approaches.