Researchers will present and discuss the fundamental topics of photobiology: How detection of light by molecular photoreceptors leads to structural changes in the photoreceptors themselves; how these changes propagate through signaling networks and across boundaries between cells to effect physiological changes at the cellular level; and ultimately, how the behavior of an organism is modified. Although photobiology largely originated in the plant sciences and is still vigorously represented there, it now embraces other experimental organisms such as bacteria, fungi, birds and humans. The field spans disciplines from biophysics and molecular biology through cellular and organismal physiology, and has very recently come to include clinical medicine. A highly applied component has recently emerged in which light is used as an active tool to modify the behavior of an organism, an approach known as “optogenetics”. Thus, the fast-moving field of optogenetics spans the range from molecular to clinical with practitioners developing, for example, molecular methods aimed at modifying the transmission of nerve impulses and the restoration of vision. Scientists studying disparate organisms speak different scientific languages, apply quite distinct experimental approaches to explore different levels of problems, and usually meet in separate conferences that tend to focus on one discipline, organism or mode of attack. Here, a major goal of this GRC is to unite the disciplines in vigorous discussion with each other. Each session will contain fewer, somewhat longer talks and will be led by a Discussion Leader whose explicit role is to present a brief overview of the topic and to stimulate discussion by participants. The GRC will consist of two poster sessions and nine oral sessions whose Discussion Leaders are indicated: Opsin-based Photoreceptor Systems (John Spudich, USA) Red-Light Sensing: Phytochrome Structure and Function (Katrina Forest, USA) Blue-Light Sensing Mediated by LOV and BLUF Domains (Aba Losi, Italy) Perception and Signaling by UV/Blue Light (Margaret Ahmad, France) Photoregulation for Biosystem Design (Arthur Grossman, USA) Integration of Light Signaling (Carlos Ballare, Argentina) The Optogenetic Toolkit (Gero Miesenboeck, UK) Breakthroughs in Photobiology (Rick Vierstra, USA) Clinical Applications of Optogenetics (Zhuo-hua Pan, USA) The closely-associated GRS will allow students, postdocs and junior researchers to present their recent work in this field, lay the scientific groundwork for fields they may be less familiar with, and offer explicit mentoring led by senior scientists in informal, round-table discussions aimed at broad aspects of career development. Note: The GRS is its own meeting and requires separate application to attend. The GRS will consist of two poster sessions, a round-table mentoring session and three oral sessions with the indicated Discussion Leaders: Signal Transduction: Photons to Networks (Ahmed El Hady, Germany) Biology of Photosensory Systems (Emilie Demarsy, Switzerland) Structural Analysis of Photoreceptors (Alex Jones, UK) Mentors: Katrina Forest (USA) and Christian Fankhauser (Switzerland)