It is thought that life began when lightning hit the sea. Lightning sent energy into the water. Chemicals in the sea were mixed together by energy. New substances, called amino acids, were made, from which life was able to grow.
The first living things on Earth were so small you could fit thousands of them on the head of a pin.
What were the first living things?
The first living things were bacteria. They lived in the sea. Some bacteria changed into algae, which were simple plants. Algae lived in the sea in masses, like huge blankets. They made oxygen, which helped to turn the sky and sea blue.