Recent advancements in genomes sequencing of members of Rickettsiaceae family have led to set a new landmark in the study of these microorganisms. Genomic analyses of Rickettsia and Orientia reveal a history of genome reduction because of the interaction with intermediate and final hosts; the evidence shows that this is an ongoing process. The gene loss, the gain, and loss of plasmids in such an easy way, among other significant processes are the evidence of the evolutionary history of this bacterial group involving reductive processes. In particular, the integrative conjugative element called REIS, was necessary in the process of adaption to an intracellular lifestyle in eukaryotes. We present a genomic focusing on Rickettsia and Orientia species, due to the animal and human importance. In this analysis, the genomic evidence shows that genomes have been extensively shuffled; however, the existence of core genes has also been conserved.