Stem cell proliferation, self-renewal and differentiation are regulated by a range of molecular mechanisms. Growth factors, transcription factors, and other components of signal transduction pathways all combine to coordinate cell behaviour. These signaling pathways can be modulated by naturally occurring and synthetic small molecules which bind to individual components of the pathway. When binding causes modification of the target molecule’s activity, the pathway can be disrupted. By targeting a particular pathway, it is possible to enhance stem cell proliferation and direct cell fate decisions. Cell Guidance Systems offers a growing range of bioactive small molecules at high levels of purity.