Fluorescent In Situ Hybridization technique (FISH) is based on the hybridization of fluorescent labeled oligonucleotide probe to a specific complementary DNA or RNA sequence in whole and intact cells.1 Microbial FISH allows the visualization identification and isolation of bacteria due to recognition of ribosomal RNA also in unculturable samples.2 FISH technique can serve as a powerful tool in the microbiome research field by allowing the observation of native microbial populations in diverse microbiome environments such as samples from human origin (blood3 and tissue4) microbial ecology (solid biofilms5 and aquatic systems6) and plants7. Prokaryotic single cell life forms are divided into two domains called Bacteria and Archaea originally categorized as Eubacteria and Archaebacteria.8 However both terms Eubacteria and Bacteria are still being used in microbiology.Eubacteria probe recognizes most bacteria as it is complementary to a portionof 16S rRNA found in almost all bacteria