The Zebrafish’s eye retina can regenerate if it is injured. If a Zebrafish is in total darkness for several days and then exposed to very bright light, all the photoreceptors in their retinas are destroyed. Due to their robust regenerative ability, however, their eyes recover in just 28 days. The retina contains a special type of adult stem cell, called Müller glia. Biology researchers at Vanderbilt University find that a drop of the brain’s neurotransmitter GABA is the trigger for regeneration. It initiates a cascade of events that includes the activation of the Müller glia and the production of various growth factors that stimulate cell growth and proliferation. This discovery raises the possibility that, by manipulating the presence of GABA, human retinas might also be induced to regenerate and reverse damage caused by diseases like macular degeneration and retinitis pigmentosa.