Whole genome sequencing, the act of deducing the complete nucleic acid sequence of the genetic code, or genome, of an organism or organelle (specifically, the mitochondrion or chloroplast). The first whole genome sequencing efforts, carried out in 1976 and 1977, focused respectively on the bacteriophages (bacteria-infecting viruses) MS2 and ΦX174, which have relatively small genomes. Since then there have been numerous innovations in the field of DNA sequencing that have expanded the capabilities of the technology. Those innovations, combined with increasing cost-effectiveness in the early 21st century, enabled the routine use of whole genome sequencing in laboratories worldwide, which effectively ushered in a new era of biological discovery.