What is the microbiome? The microbial community? Does it include viruses? There are conflicting informations about the definitions of the microbiome in the literature. An initiative organized by MicrobiomeSupport and led by AMICI expert Gabriele Berg has thus revisited the definition of the term microbiome. The commentary Microbiome definition re-visited: old concepts and new challenges in the journal Microbiome is co-authored by several AMICI experts.