A significant portion of innovative medicines originate from phenotypically active molecules. Understanding the molecular target mechanisms of such molecules is crucial for further developing them into useful medicines. Research activities in the Feng lab focus on identification and validation of small molecule targets by applying technologies at the interface of biology and chemistry. In the past decade, we have been involved in developing a series of novel technologies, including high-content phenotypic screening and profiling, affinity proteomics-based target expansion, and drug resistance screens in mammalian cells, combining mutagenesis, next-generation sequencing and gene-editing tools. We have successfully applied these technologies to identify and validate targets for important bioactive small molecules. Currently, we are particularly interested in understanding the target mechanisms of novel small molecule modulators of the innate immune response and cellular metabolism.