Water seems like a simple thing. You drink it, wash with it, and swim in it. But water is actually made of two different elements mixed together: hydrogen and oxygen. For a long time, scientists wondered if they could take water apart. On May 2, 1800, two British scientists named William Nicholson and Anthony Carlisle found a way. They used a brand-new invention called a battery. They connected wires from the battery to two metal strips and placed the strips in a bowl of water. When the electricity flowed, something amazing happened. Tiny bubbles appeared on each metal strip. The bubbles on one strip were hydrogen gas. The bubbles on the other were oxygen gas. The electricity was pulling the water apart into its components. This process was called electrolysis. The experiment was groundbreaking for two reasons. First, it proved that water was not a single substance. It was two elements combined. Second, it showed that electricity could cause chemical changes. Before this, scientists thought electricity was only useful for sparks and shocks, but Nicholson and Carlisle showed it could rearrange the building blocks of matter.