Self-cleaning windows.

A Reuters story this morning discusses photocatalysts, substances that react with light and oxygen to break down organic compounds, such as soot particles. Coat a wall or a window with these substances, and you’ve got a self-cleaning surface. They’re attracting a lot of attention in Japan, but haven’t caught on elsewhere. I don’t see why not — self-cleaning windows and air-purifying walls sound like a great idea to me!