Looking back one, two and five years ago today on Worldchanging:

2009
The Bioluminescent Metropolis
Geoff Manaugh explores the idea of cultivating bioluminescent organisms for use in future architectural ornament and city planning...

2008
Reader Report: China's Green Beat
Jamie Henn reflects on China's sustainable future now that the 'green' Olympics have ended...

2005
Retro: Human Changing
Three excellent books about the transformation of what it means to be human came out in the past year: James Hughes' Citizen Cyborg, Ramez Naam's More Than Human, and journalist Joel Garreau's Radical Evolution. The three authors have varied but complementary ideas about what human augmentation might entail, and agreed to a collective interview...

Other recent "look backs":
August 23
August 24
August 25