The purpose of this funding opportunity announcement (FOA) is to support collaborative pilot research projects focused on potential effects relevant to human health of chemically complex natural products and/or the causal, molecular mechanisms underlying such effects. A critical element of each proposed project must be collaboration with one or more of the NIH Centers for Advancing Research on Botanicals and Other Natural Products (CARBON). More specifically, letters of support describing collaboration with one or more of the U19 Botanical Dietary Supplements Research Centers awarded in 2020 must be included at the time of submission. Each proposed pilot project must, with agreement of its collaborating Center(s), leverage products used in those Centers to extend understanding of their biological effects, or of their causal, molecular mechanisms of action, or increase understanding of other chemically complex natural products through use of methods developed and used in the Centers. Research approaches may range from bench through in vitro and non-human animal models to, where feasible and appropriate, obtaining additional feasibility or outcome information from clinical trials being performed by the CARBON awardees, either through inclusion of additional measures or through secondary analysis of data or specimens.