Why do star twinkles night?

Twinkle Twinkle little star.i think probably all of us have heard this nursery rhime ones.i also use to sing this rhime in my childhood but have you wonder how stars twinkle.                                                                  Stars twinkle at night due to continous atmospheric reaction. light comming from star to earth experiences multiple refraction.Earth has different layer of atmosphere .when light enters in earth atmosphere it experiences continous atmospheric refraction.even temperature and pressure in atmosphere changes time and again. so every light ray comminh towards earth refract differently in different direction.it fluclutes the appearent position of star.Twinkilng is not by the star but by the change in apparent position of star continously.