I remember reading a story in my English Textbook titled “The Country of the Blind”. It left quite an impression. In the story, the author talks about a secluded country in which all the citizens are blind. They have different habits – for example they would perceive the world by touch, smell and feel. So, the people were active at night when it was cooler and would sleep during the day when it was warmer. Our bodies are in sync with the environment by our biological clock, body thermostat or Circadian rhythms. The clock signals sleep and wake-up time. But now we have a multitude of man-made-signals that interfere with this age-old mechanism. One of them is the screen light of our electronic devices that tells our bodies that it is still daylight. Consequently, we keep pushing sleep, and wake up tired and sleepy the next day – sometimes even after what we might call adequate number of sleep hours. If I read a book at bedtime, I feel sleepy earlier; reading on my cell-phone, as this article says, would postpone my sleep time.