There are people out there who can read minds.
Well, sort of.
Your face is an open book, and even the best poker face can't hide involuntary movements.
Microexpressions are involuntary contractions of facial muscles. They're caused by the same muscles that we use to make normal expressions we're familiar with. The problem is, they happen at fractions of a second, so they're almost imperceptible.
The TV show, Lie to me, is an amazing insight into the science and the usage of microexpressions to detect lies and otherwise understand humans. The main character is based on the real-life of Paul Ekman, who codified the human face and the muscles within it to be able to characterise human emotions and expressions.
He found that there are 7 universal human facial expressions: Anger, Disgust, Fear, Surprise, Happiness, Sadness and Contempt.
No matter where you go, or who you speak to, you'll see the same micro-expressions on everyone.
Why does this matter? You can use even a basic understanding of microexpressions in every conversation, every negotiation, almost every situation you find yourself in.
Looking at unedited video footage shows the most prominent examples of microexpressions. Bill Clinton is a perfect muse. A 40-second clip of his deposition shows so much emotional leakage it's laughable when you know what you're looking for.
The human face is easy to read when you know how.
It's a window into the brain, and learning to perceive these cues will change your life.