The fundamental understanding of molecular quantum electrodynamics via the strong light–matter interactions between a nanophotonic cavity and quantum emitters opens various applications in quantum biology, biophysics, and chemistry. However, considerable obstacles to obtaining a clear understanding of coupling mechanisms via reliable experimental quantifications remain to be resolved before this field can truly blossom toward practical applications in quantitative life science and photochemistry. Here, we provide recent advancements of state-of-the-art demonstrations in plexcitonic and vibro-polaritonic strong couplings and their applications. We highlight recent studies on various strong coupling systems for altering chemical reaction landscapes. Then, we discuss reports dedicated to the utilization of strong coupling methods for biomolecular sensing, protein functioning studies, and the generation of hybrid light–matter states inside living cells. The strong coupling regime provides a tool for investigating and altering coherent quantum processes in natural biological processes. We also provide an overview of new findings and future avenues of quantum biology and biochemistry.