I also learnt from this article that we can apply self-acupressure on the yintang.
"To apply acupressure to Yin Tang, bring the first and middle fingers of your two hands together, using the ends of those four fingers, in concert, to very gently, in a circular motion, massage the area between the inner ends of your two eyebrows. The motion can be either clockwise or counter-clockwise (find out which intuitively feels best to you). As you apply that circular acupressure/massage, allow all the muscles of your forehead to soften and relax (saying "ahh" can be useful here), as though they were releasing backward, in the direction of the center of your skull (the upper dantian area)."
When googling "yintang acupuncture youtube", I came across this fun and edutaining video on the extra points in acupuncture, including the yintang point.
I also find this information on this related article useful regarding how yintang or the pineal gland can be stimulated to secrete the hormone melatonin which makes us sleepy.
http://cuppingforlife.This article says that research results showed "similarities measured in the human brain both under sedation using yintang and sedation using anesthesia."
blogspot.sg/2011/11/yintang- most-requested-acupuncture. html
"The location of this acupuncture point corresponds to the third eye, a metaphoric eye in Hinduism and Buddhism that opens as our consciousness expands and we become enlightened. It is the location of the brow chakra, the 6th of 7 major energy vortexes that exist in our bodies, which has to do with inner guidance, mental clarity, and intuition. Even in western medicine this is an anatomically important location, where light enters the skull to activate the pineal gland. As darkness increases in the evening, the pineal gland is stimulated to secrete the hormone melatonin, which makes us sleepy. As the sun comes up and light increases, the pineal gland stops producing this hormone and we wake up."
"The journal Medical Acupuncture published a 2005 study entitled “Shenting and Yintang: Quantification Of Cerebral Effects Of Acupressure, Manual Acupuncture, and Laserneedle Acupuncture Using High-Tech Neuromonitoring Methods,” by Gerhard Litscher, MDsc. The study was about the electroencephalographic similarities of acupressure induced sedation and general anesthesia, as assessed by bispectral index and spectral edge frequency. Read the study here. The basic result showed similarities measured in the human brain both under sedation using yintang and sedation using anesthesia."