smile is a 
facial expressionformed by flexing those 
muscles most notably near both ends of the 
mouth. The smile can also be found around the 
eyes. Among 
humans, it is 
customarily an expression denoting 
pleasure, happiness, or 
amusement, but can also be an involuntary expression of 
anxiety, in which case it is known as a 
grimace. Cross-cultural studies have shown that smiling is used as a means of communicating emotions throughout the world. Happiness is most often the motivating cause of a smile. Among 
animals, the exposure of 
teeth, which may bear a resemblance to a smile, is often used as a 
threat or warning display  known as a 
snarl or a sign of 
submission. In 
chimpanzees, it can also be a sign of 
fear. The study of smiles is a part of 
gelotology, psychology, and linguistics, comprising various theories of affect, humor, and laughter.
we're always smile like nuthink wrong... make people appy with us... we're always care of other's heart,, but who want to care 'bout our heart?? hmm... life is not always perfect... peace...