In this episode, I host Dr. Samer Hattar, Chief of the Section on Light and Circadian Rhythms at the National Institute of Mental Health. Dr. Hattar is a world-renowned expert on how viewing light at particular times adjusts our mood, ability to learn, stress and hormone levels, appetite, and mental health. We discuss how to determine and use your individual light sensitivity to determine the optimal sleep-wake cycle for you. We also discuss how to combine your light viewing and waking time with the timing of your food intake and exercise in order to maximize mental and physical functioning. Dr. Hattar is credited with co-discovering the neurons in the eye that set our circadian clocks and regulate mood and appetite. He explains why even a small shift in daylight savings leads to outsized effects on our biking because of the way that our cells and circadian clocks integrate across many days. And he offers precise tools to rapidly adjust to jetlag, shift work, and reset your clock after a late night of work or socializing. This episode is filled with cutting-edge data on the biological mechanisms of human physiology and practical tools for people of all ages.    Thank you to our sponsors: ROKA - https://www.roka.com -- code: "huberman" InsideTracker - https://www.insidetracker.com/huberman  Magic Spoon - https://www.magicspoon.com/huberman    Support Research in Huberman Lab at Stanford: https://hubermanlab.stanford.edu/giving   Our Patreon page: https://www.patreon.com/andrewhuberman    Supplements from Thorne: http://www.thorne.com/u/huberman    Social: Instagram - https://www.instagram.com/hubermanlab  Twitter - https://twitter.com/hubermanlab  Facebook - https://www.facebook.com/hubermanlab  Website - https://hubermanlab.com  Newsletter - https://hubermanlab.com/neural-network    Samer Hattar: Twitter: https://twitter.com/samerhattar  Instagram: https://www.instagram.com/samerhattar  Wikipedia: https://en.wikipedia.org/wiki/Samer_Hattar    Links: Graphical Explanation of Temperature Minimum for Overcoming Jetlag - https://www.instagram.com/tv/CKWiRVJHVwC   Timestamps: 00:00:00 Introducing Dr. Samer Hattar, Ph.D. 00:02:17 Sponsors: ROKA, InsideTracker, Magic Spoon 00:06:15 Light, Circadian (24 hour) & Circannual (365 day) “Photoentrainment”  00:14:30 Neurons in Our Eyes That Set Our Body Clocks: Similar to Frog Skin 00:18:55 What Blind People See  00:20:15 When, How & How Long to View Light for Optimal Sleep & Wakefulness 00:30:20 Sunlight Simulators, Afternoon Light Viewing, Naps 00:33:48 Are You Jetlagged at Home? Chronotypes & Why Early Risers Succeed  00:38:33 How to Decide Your Best Sleep-Wake Schedule; Minimal Light Test 00:42:16 Viewing Light in Middle of Day: Mood & “Light Hunger” 00:44:55 Evening Sunlight; Blueblocker Warning 00:48:57 Blue Light Is Not the Issue; Samer’s Cave; Complete Darkness 00:53:58 Screens at Night 00:56:03 Dangers of Bright Light Between 10 pm and 4 am: Mood & Learning 01:01:05 The Tripartite Model: Circadian, Sleep Drive, Feeding Schedules 01:05:05 Using Light to Enhance Your Mood; & The Hattar-Hernandez Nucleus 01:07:19 Why Do We Sleep? 01:08:17 Effects of Light on Appetite; Regular Light & Meal Times 01:18:08 Samer’s Experience with Adjusting Meal Timing 01:22:51 Using Light to Align Sleep, Mood, Feeding, Exercise & Cognition 01:30:15 Age-Related Changes in Timing of Mental & Physical Vigor   01:31:44 “Chrono-Attraction” in Relationships; Social-Rhythms 01:33:40 Re-setting Our Clock Schedule; Screen Devices Revisited 01:37:50 How Samer Got into the Study of Light  01:39:33 Clock Gene mRNAs & More Accurate Biomarkers 01:41:08 Light as Medicine 01:42:48 ADHD (Attention-Deficit Hyperactivity Disorder)  01:43:35 How to Beat Jetlag: Light, Temperature, Eating 01:50:44 Vigor: The Consequence of Proper Timing  01:52:15 Waking in the Middle of the Night: When Your Nightly Sleep Becomes a Nap 01:54:10 Melatonin, Pineal Calcification 01:55:25 Our Seasonal Rhythms: Mood, Depression, Let