The application of small molecules to study a biological system is referred to as 'Chemical Biology'. Typically, these molecules interfere with the function of target proteins and consequently lead to disruption of biological processes. When these molecules are applied to cells or whole organisms, the consequences of this perturbation can be studied at the molecular level. As such, these chemical probes allow researchers to unravel the role of cellular and molecular components in a complex biological network, even inside living organisms. Next to the application as chemical probes, small molecules can also be used as starting points for the development of therapeutic agents to treat disease or, in the field of plant sciences, of plant-protective substances.