After learning and getting all excited about volcanoes, the children were introduced to the next era in the History of the Earth -- the Proterozoic Era, where the first life began.
Oceans were formed then due to consistent rain over many years. Micro-organism started to grow in the water and it was the first life seen on Earth. Algae was one of the first few plants appeared in that era. Hence, we let the children grow Algae in a tank.
Auntie Shirin brought in the sand and algae, and showed children how to plant it in the water. The children were excited about putting water into the tank (see video below). They also touched the algae, which was at that stage in a rough hairy state.
After they have planted the algae in the tank for a few days, the algae turned slimy. Again, the children touched the algae and felt the difference. This stimulated the young minds in awe in terms of how the state of a living thing changed after being nourished by water and sunlight.