Building of solar system.
Our solar system was formed billions of years ago when the solar nebula collapsed, and this was the first step towards the formation of solar system.
Solar nebula is simply a large cloud or body of dust and gas. According to the studies conducted by scientists, solar nebula formed when a large body of cloud deflated, the reason must be because of the shockwave which resulted from the close explosion of the star, which is called supernova.
Later, various hydrogen atom began to merge, thus forming helium and the release of that energy resulted in the formation of Sun. This way many other planets began forming giving rise to solar system.