Our understanding of bacterial vaginosis (BV) has evolved over many years, yet the condition remains mysterious. BV has been described as a complex microbial imbalance, with the native vaginal Lactobacillus species and increased anaerobic bacteria playing significantroles. Today, BV is understood as dysbiosis of the vaginal microbiome, whether symptomatic or asymptomatic. The condition is common, but despite years of study, the lack of an exact cause—and why some women get it and others do not—adds to its mystery. In 2017, however, an innovative single oral dose treatment emerged that may reduce incidence.