Willson has been a long-time supporter of precompetitive chemistry as a mechanism to bring innovation to early drug discovery. His team has made potent and selective chemical probes for orphan nuclear receptors widely available in the scientific community. He was a scientific founder of the SGC Epigenetic Chemical Probes project that led to the release into the public domain of more than 30 chemical probes that specifically inhibit enzyme modifiers and protein readers of the histone tails. Willson started a program to develop chemical probes for the understudied protein kinases that has made a set of more than 800 kinase inhibitors freely available to academic researchers. The open availability of these chemical probes has had widespread scientific impact through their use as tools to study the biology of their cognate proteins.