Urey and Miller famously recreated the conditions of early Earth in their laboratory. This was a simulated primordial soup that they believed could have been the environment where life first arose.

Specifically, they:

* Created a closed system with water vapor, methane, ammonia, and hydrogen gas (which they believed were the main gases present in the early Earth's atmosphere).

* Simulated lightning strikes using electric sparks.

* Allowed the mixture to cool down to form a liquid.

The result was the formation of organic molecules like amino acids, which are the building blocks of proteins, essential for life.

This experiment was groundbreaking, as it offered evidence that the building blocks of life could have formed naturally under conditions that existed on early Earth.