The Sun possesses a number of fundamental physics questions, including the existence of the hotter upper atmosphere (> 1 MK) above the cooler photosphere (~ 6000 K) and continuous streaming of ionised plasma in the heliosphere in the form of solar wind. Due to such higher temperatures in the atmosphere, the Sun emits Ultraviolet and X-ray radiations, which have substantial implications for the dynamics of the Earth's atmosphere and sun climate. Moreover, the solar wind creates space weather effects that may be hazardous to humankind. In this talk, after giving a brief overview of some of the open questions, I will discuss a possible unified scenario that we have proposed for the formation of solar wind and the heating of the corona.