 Walking into a room bathed in white light can be pretty jarring. There's a good reason for that. In 2002, scientists discovered specialized cells in the eye that are specifically tuned to the bluish end of the visible spectrum. The part that makes harsh white light, well, harsh. These cells are also hardwired to the part of the brain that controls our sleep cycle. So white light functions as a sort of alarm to our internal clock. Now, researchers are learning how to use lighting design to hack this physiological system for one of the environments where it's needed most, the drowsy morning classroom. Researchers from the Korea Advanced Institute of Science and Technology expose 15 healthy young students to different lighting conditions. Warm light, the yellowish kind, typically associated with the soft glow of incandescent bulbs, and cool, blue-enriched white light. Saliva samples were taken before and after each light exposure to assess levels of melatonin and cortisol, the hormones that regulate sleep. Melatonin signals when it's time to go to sleep and drops in the morning when it's time to wake up. Cortisol increases shortly after awakening. Whilst the team observed no effects on cortisol levels, they did find that melatonin concentrations were sensitive to the type of light the students were exposed to. Compared to warm light, blue-enriched white light led to a significantly greater decline in melatonin secretion. Additionally, the team found that morning exposure to blue-enriched white light significantly improved students' perception of alertness and it positively affected their mood and visual comfort. These findings suggest that LED light curbed toward the blue end of the spectrum could be an effective countermeasure for morning drowsiness, especially in indoor spaces with insufficient daylight. The authors of the study hoped to translate their findings beyond the classroom to tailor the physiological effects of lighting to different spaces and different lifestyles.