The oral cavity hosts a diverse range of microorganisms that are essential for maintaining oral and general health. These communities include bacteria, fungi, archaea, viruses, and protozoa, and they inhabit distinct niches within the oral cavity. While most research has been dedicated to the study of bacteria, knowledge regarding the acquisition and maintenance of other members of the oral microbiota is still scarce. This chapter aims to explore the process of oral microbiota acquisition from the prenatal to the postnatal stages, emphasizing the intricate interplay between host and environmental factors that shape these microbial communities. However, it is important to acknowledge that significant gaps in knowledge persist, particularly regarding the understanding of these processes beyond bacteria.