Recent work has demonstrated that our skin-associated bacterial communities are surprisingly diverse, with a high degree of interindividual variability in the composition of bacterial communities at a particular skin location (5–9). For example, only 13% of the bacterial phylotypes on the palm surface are shared between any two individuals (8), and a similar level of interpersonal differentiation is observed at other skin locations (5, 9). In addition, skin bacterial communities are relatively stable over time: palm surface bacterial communities recover within hours after hand washing (8); and, on average, interpersonal variation in community composition exceeds temporal variation within people, even when individuals are sampled many months apart (5, 9). Given that individuals appear to harbor personally unique, temporally stable, and transferable skin-associated bacterial communities, we hypothesized that we could use these bacteria as “fingerprints” for forensic identification.