For this experiment, Miller designed a sealed glass apparatus and used it to simulate the conditions on Earth before life appeared. It had two two glass flasks. One was of 500ml with 200 ml of water poured in it. The other was of 5 liter with a pair of electrodes. This one was filled with 100 mmHg of Hydrogen (H, 200 mmHg of Methane (CH), and 200 mmHg of Ammonia (NH). To simulate rain, the water in the smaller flask was heated to create evaporation, and the water vapour was allowed to enter the larger flask and it mixed with the other gases. To simulate lightning in the water vapour and gaseous mixture, electrical sparks were fired between the electrodes. Then the water was cooled again and the water created rain. This process continued for a week.