The establishment of the infant gut microbiota is a highly dynamic process dependent on extrinsic and intrinsic factors. We characterized the faecal microbiota of 4 breastfed infants and 4 formula-fed infants at 17 consecutive time points during the first 12 weeks of life. Microbiota composition was analysed by a combination of 16S rRNA gene sequencing and quantitative PCR (qPCR). In this dataset, individuality was a major driver of microbiota composition (P = 0.002) and was more pronounced in breastfed infants. A developmental signature could be distinguished, characterized by sequential colonisation of i) intrauterine/vaginal birth associated taxa, ii) skin derived taxa and other typical early colonisers such as Streptococcus and Enterobacteriaceae, iii) domination of Bifidobacteriaceae, and iv) the appearance of adultlike taxa, particularly species associated with Blautia, Eggerthella, and the potential pathobiont Clostridium difficile. Low abundance of potential pathogens was detected by 16S profiling and confirmed by qPCR. Incidence and dominance of skin and breast milk associated microbes were increased in the gut microbiome of breastfed infants compared to formula-fed infants. The approaches in this study indicate that microbiota development of breastfed and formula-fed infants proceeds according to similar developmental stages with microbiota signatures that include stage-specific species.