Bikes Of May

Pocket-Sized Bikes
Fold-up bicycles neatly line the sidewalk at a bicycle festival hosted by TIME's UP!. The Brompton models pictured here can be folded up in less than a minute and boast one of the smallest dimensions on the market. Other brands and models are triangular, some circular and some feature teeny-tiny wheels. The concept doesn't end with bikes either; riding enthusiasts have even carried the notion to bike accessories. Witness the "Stash Helmet".

• How to Win the War on Global Warming