Origin of the universe:
1) In the begining there was a tiny dot that trapped in a lot of energy there in. The dot is a matter. NB: first law of thermodynamics, matter can neither be created nor destroyed.
2) Because of the trapped energy maybe. There was an expansion(bigbang)

3) This brought about the universe. The young universe was so hot, it cools as it expanded. Guess what!! Its still expanding till today
4) The expansion of the universe gives way for formation of different atoms.
5) The planet and galaxies formed. They are mainly fussion of ...

Hydrogen molecules and helium atom.
Follow to know how different species we see on earth came abt scientifically.