Serial saliva sampling is a method used in our lab and to determine when melatonin, a hormone related to our biological clock (circadian rhythm), is released at night. Every thirty minutes for six hours in the evening before participants go to sleep, participants place a small cotton plug in their mouth to saturate it with saliva. This plug is then placed in a cotton tube and sent away for testing.
Light levels in your room will be kept dim, because bright light suppresses the release of melatonin that occurs naturally in dim-light evening conditions.