At first, Claude did not think about a neon lamp. He wanted to extract pure oxygen to sell it to hospitals and welders. But the oxygen kept coming with a retinue of inert gases. Driving the unwelcome guests into tubes under low pressure, he discovered that the tubes were glowing: those with neon were glowing red, while tubes with argon generated blue light. That was when the entrepreneur's head came aflame. And the streets in cities and towns lit up.