In one sentence, describe what the following article is about:

Charles Darwin (1872) was the first to suggest that the facial expressions of certain emotions were universal. Studies in his time were inconclusive; however, research continued on the subject, and in the 1960s Silvan Tomkins conducted the first study demonstrating that facial expressions are in fact reliably associated certain emotional states. Studies have shown that when emotions are spontaneously aroused, congenitally blind individuals produce the same facial expressions as sighted individuals do. In addition, facial expressions considered to be universal in humans have also been observed in non-human primates, particularly chimpanzees. A face expressing happiness or joy will feature a smile (corners of the mouth drawn up and back) with some teeth exposed, and a wrinkle runs from the outer nose to the outer corners of the lip. The cheeks are raised, and the lower eyelids are tense or wrinkled. The narrowing of the eyelids causes “crow’s feet” wrinkles at the outer corners of the eyes. A face that is smiling but does not involve the muscles in the eyes indicates a fake smile or polite smile that is not actual happiness or joy. A face showing sadness has the eyebrows drawn in and up, the skin below the eyebrows is triangulated with the inner corner up, and the corners of the lips are turned down. The jaw comes up and the bottom lip pouts out. Studies show that this emotion is the hardest expression to fake. A face showing contempt, or hate, has one corner of the mouth rising, like a sort of half-smile which is actually a sneer. A disgusted face has the eyebrows downcast, but the lower eyelid raised (causing the eyes to narrow), the cheeks are raised and the nose is scrunched. The upper lip is also raised or curled upward. A surprised face features the eyebrows raised up and curved. The skin below the brow is stretched and there are horizontal wrinkles across the forehead. The eyelids are so wide open that the whites are showing above and/or below the pupils. The jaw is dropped and teeth are slightly parted, but there’s no stretching or tension of the mouth. A face showing fear has raised eyebrows that are usually more flat, not curved. There are wrinkles in the forehead in the center between the brows, not across. The upper eyelids are raised, but lower eyelids are tense and drawn up, usually causing whites to show in the upper eye but not lower. The lips are usually tensed or drawn back, the mouth may be open and nostrils may be flared. An angry face will show eyebrows that are lowered and drawn together, eyes staring hard or bulging, with vertical lines appearing between the brows and the lower eyelids tensed. Nostrils may be flared, and the mouth is either firmly pressed together with the lips drawn down at the corners, or in a square shape as if shouting. Also, the lower jaw juts out.

Summary:
Think about the link between emotions and expressions. Learn to read happiness. Identify sadness. Learn to read contempt. Identify disgust. Watch for surprise. Notice fear. Identify anger.