Metagenomics, the analysis of the microbial genome, permits scientists to understand the influences of external sources including diet, metabolism and antibiotics on the human microbiome. Research has revealed the possibility of a core symbiosis between humans and bacteria. The main role of the human microbiome is to aid in digestion, but identified ancillary roles include immunologic homeostasis and infection prevention. Quantifying the composition and variability of the microbiome will help lead to future treatments or preventive strategies against unhealthy change. A variety of methods may be used to define the microbiome, and 16S amplicon sequencing is primarily utilized today. Probiotics positively influence the microbiome by altering levels of pro-inflammatory and anti-inflammatory cytokines. Pharmacists can provide a role in metagenomics by counseling patients on the proper diet and probiotic consumption.