Photochromic ligands, molecules that can be induced to change their physical properties through applied light, are currently the topic of much chemical biology research. This specialized class of small organic structures are, surprisingly to many, fairly common in nature. At the core of a number of natural biological processes lies a small molecule that changes shape or some other measurable property in response to light absorption. For instance, conformational changes invoked by reversible photoisomerization of a retinoid small molecule found in the photoreceptors of the human eye leads to vision. In plants, photoisomerization of a cinnamate moiety leads to altered gene expression. The photosensitive molecule can be viewed simply as a nanosensor of light, much like a photosensitive electrical component might be added to a circuit to sense day versus night to turn an electrical circuit on or off. Synthetic organic chemists and chemical biologists have been, for at least the last 15years, trying to either mimic or exploit the native photochromism found in nature. Here, we describe the design process to develop a photochromic molecule to be used in neurobiology.