Cas9 is the genome editing tool of choice for a number of model organisms: mammalian cells, yeast, drosophila, plants, worms, zebrafish, frogs, some bacteria; but not thermophilic (high heat loving) bacteria. Until recently the only available Cas9 proteins were isolated from mesophilic (medium heat loving) bacteria, such as Streptococcus pyogene’s SpCas9. These Cas9 proteins don’t work well at high temperatures, so to use them in thermophiles, bacteria must be grown at lower temps. This approach only works for facultative thermophiles (high OR medium heat loving), but not obligate thermophiles. However, the recent discovery of GeoCas9 by the Doudna lab has opened up the field of thermophilic bacteria to CRISPR/Cas9 genome editing.