The Big Bang created most of the universe through, Big Bang Nucleosynthesis which created most of the lighter elements with a mass number below 3 such as hydrogen and helium, which then formed the first stars and subsequently formed the first nebula. While they fused material in extreme temperatures the resulting energy would change the natural abundances of chemical elements which would later create other heavier elements, however not all of them. When their lifespan ran short and they went supernova (specifically type II) they generated so much heat in the resulting explosion that Supernova Nucleosynthesis occurred. Similar to Big Bang Nucleosynthesis except that it already had the lighter elements in the mix which would fuse into the heavier elements we see today like Uranium. Nucleosynthesis is the formation of new atomic nuclei from present material which requires a lot of heat and energy for it to occur, hence why it occurs in stars. And the resulting material that was shot from the stars directly after Nucleosynthesis occurred went on to form other planets and galaxies, when they themselves formed into other stars. And through Stellar Evolution they either evolved into other Planetary Nebula and eventually White Dwarfs or went Supernova and became the black holes or neutron stars we see at the center of galaxies today(just the black holes). The perpetual action of nebulae eventually formed our planets when the solid matter coagulated and formed rocky planetesimals; which would eventually form planets through forces such as tectonics, gravity, weathering, erosion, and celestial collisions.
