Many organisms regulate gene transcription via sunlight. In plants, phototaxis, flowering and germination all are light dependent processes. Circadian rhythms in many species is entrained by light. Light-activated transcription is achieved through a variety of mechanisms. Some of these mechanisms may be usable as a powerful tool to control gene expression in selected cells with high spatial and temporal resolution. When paired with other optical tools, such as genetically-encoded calcium indicators or channelrhodopsins, this technique would give unprecedented specificity in recording and manipulating brain activity. In this journal club, I review two major systems for photoactivateable transcription and their prospects for application in mammalian systems.