Optical frequency combs are precise rulers which have been used for applications such as optical clocks and spectroscopy. Generating on-chip microcavity optical frequency combs for biological and chemical applications is an emerging area that is poised to have an impact throughout the optics and photonics community by significantly improving the sensitivity and specificity of biochemical sensors. The application of frequency comb technology to biology, chemistry, and medicine can lead to advances in molecular diagnostics as well as an improved understanding of disease mechanisms.