The developmental journey from birth, through infancy, childhood and into adulthood is a complex one, not least for the trillions of bacteria residing in our gut, the so-called gut microbiome. The gut microbiota is a highly complex community which evolves and adapts to its host over a lifetime and is integral to the health of its host, serving a myriad of functions, from providing essential nutrients, prevention of pathogen colonisation, immune functioning to interactions within the brain through the gut-brain microbiome axis. The study of the gut microbiome has been revolutionised over the last 15 years by advances in genetic methods and sophisticated bioinformatic tools. Next generation sequencing (NGS) is a low-cost, high-throughput sequencing platform that enables analysis of all the genomes within an ecosystem sample (shotgun metagenomics), or a description of the taxa within a given community by sequencing conserved marker genes such as the 16srRNA gene of bacteria and archaea. We have been interested for a number of years in studying the gut microbiome in early life and uncovering the plethora of factors that impact the bacteria an infant acquires at birth and in early life. In this study, we sequenced DNA from faecal samples of children over the first four years and found that there is a perpetual evolution of the gut microbiota during this period.