Formation of the planets
The planets are all different. Some probably formed mainly from colliding specks of dust, and others from collapsing blobs of gas and dust.

How was the Earth formed?
Scientists believe that the Earth formed from dust particles that clumped together to form lumps, which collided and formed larger lumps and clusters, gradually building into a planet. Temperatures rose to more than 5000 Celsius (9000 Fahrenheit), enough to melt the Earth into a churning cauldron. As he Earth started to cool, the surface formed a rocky crust. But deep inside the Earth, temperature are still 4500 Celsius (8100 Fahrenheit) and the rocks are molten, rising to the surface most spectacularly when a volcano erupts.