John Doerr knows a good investment when he sees it. He bet on firms like Netscape, Amazon.com, and Google, before they became household names, and built a multi-billion dollar venture capital business. So what does John Doerr see as the next big thing?

"This field of greentech," he says, "could be the largest economic opportunity of the 21st century."

And he's putting his money where his mouth is. His firm, Kleiner Perkins Caufield & Byers, is pumping $100 million into technologies that help provide cleaner energy, transportation, air and water.

But that's peanuts compared to what Google founders Sergey Brin and Larry Page announced earlier this summer with their plans to invest in what will be the world's largest solar cell production plant. The project, by the nanotechnology whiz kids at NanoSolar, will triple the country's solar cell production capacity when it comes on line in 2007.

What this means is that green technology is no longer on the virtuous fringes of the economy. It's big business. And moguls like Doerr, Brin and Page see big profits.

But for investors and consumers alike, embracing green tech may not be easy. Technology, after all, has spent the last fifty years playing the bad guy, ruining the planet for us and the generations to follow. Technology, however, is not the cause of our environmental problems, simply a powerful tool we've misused to create them. Now, as we recognize our mistakes and perhaps begin to correct them, we have the opportunity to use the power of technology to repair the harm we have done.

Nowhere is the vision of technology in the service of sustainability more promising than in the field of nanotechnology. This emerging science, which deals with matter at the scale of a billionth of a meter, is revolutionizing industries from energy to automotive, from cosmetics to agriculture. The National Science Foundation estimates that by 2015 nanotechnology will have a $1 trillion impact on the global economy. And the Interagency Working Group on Nanoscience, Engineering and Technology says, "Nanotechnology is likely to change the way almost everything-from vaccines to computers to automobile tires to objects not yet imagined-is designed and made."

In fact, it is already transforming these industries, and there is every indication that the transformation is a green one. From radical pollution-free fuel cells to smog-eating nanocoatings, nanotech is making some startling advances on the green frontier.

"Preserving our environment should be top priority," says Robin Low, CEO of Greenyarn, one of the new companies marketing the green potential of nanotechnology. "Every company needs to minimize pollution and make products that do not harm the environment."

Greenyarn develops advanced materials for consumers seeking eco-friendly alternatives to conventional fabrics. Their Eco-fabric is a material that contains nanoparticles of bamboo-charcoal, combining all natural cloth with the properties of bamboo.

To keep tabs on the green nanotech movement, hook in to the Woodrow Wilson International Center for Scholars' GreenNano series. The series aims to advance development of clean technologies using nanotechnology, to minimize potential environmental and human health risks associated with the manufacture and use of nanotechnology products, and to encourage replacement of existing products with new nano products that are more environmentally friendly throughout their lifecycle. The centers webcasts offer a rich introduction to green nanotech.

If Doerr is right, and green technology proves to be the largest economic opportunity of the 21st century, it may just be nanotechnology that leads the revolution.

George Elvin is the President of Nanosearch, a research and advising firm on nanotechnology in the building industry, an Associate Professor in the College of Architecture and Planning at Ball State University, and a Senior Research Associate at the Building Futures Institute.