The Sun's atmosphere consists of several layers, primarily the photosphere, chromosphere, and corona. The photosphere is the visible surface of the Sun, where sunlight is emitted. Above it lies the chromosphere, a thin layer that can be seen during solar eclipses, and the corona, which is the outermost layer extending millions of kilometers into space. The temperature and density of the Sun's atmosphere vary significantly. The photosphere is relatively cool at about 5,500 degrees Celsius, while the corona reaches temperatures of over 1 million degrees Celsius. This temperature difference is a key area of research in understanding solar phenomena like solar flares and coronal mass ejections.