At first, small stars called microplanets collided with each other, merged, and gradually grew to the size of a star.
When the Earth was first born, it was not round like today's Earth, and there were craters everywhere, like those on the Moon.
There was something like air, but the oceans had not yet formed. Later, volcanic activity increased, and volcanoes exploded here and there, spewing lava onto the ground.
The lava first covered the bumpy surface of the earth. Then, the action of water made the earth round. Rainwater gradually eroded away the bumpy areas of the earth, and then washed away the soil and sand that had been eroded away to fill in the lower areas of the earth. In this way, the earth gradually became round, little by little.