"There has been more material progress in the United States in the 20th century than there was in the entire world in all the previous centuries combined."
-- Stephen Moore and Julian Simon, Cato Institute, December 1999

Given the success of the 20th century, those of us living in the 21st century have come to expect constant improvements in technology.

But this culture of constant expectation is a relatively new phenomenon in human history. In terms of technology, your great-great-grandfather's life in the 19th century wasn't that much different than his great-great-grandfather's before him. In fact, the two could have switched times and places and still functioned with relative ease. But try putting one of them here in the 21st century. Talk about a fish out of water! Things we accept as commonplace today -- commercial airplanes, television, and microwave ovens -- would be downright perplexing to them.

And to think, all of these world-changing advances took place in just the 20th century. Heck, in a mere 66 years, we went from the Wright Brothers' first flight to Neil Armstrong setting foot on the moon. That's absolutely incredible when you think about it in the context of human history.

So what's next?
If the first eight years of this century are any indication, 21st-century innovation will prove to be even more prolific than that of the 20th. Consider the impact that in-car navigation systems, produced by companies like Garmin (NASDAQ:GRMN), have had on the way we travel, or how a free website like Craigslist.com has become a major competitor of online titans like eBay (NASDAQ:EBAY)

Rapid technological advances are also being made in the health-care industry. In 2006, for instance, Atripla, the once-a-day HIV-fighting pill from Gilead Sciences (NASDAQ:GILD) and Bristol-Myers Squibb (NYSE:BMY), received FDA approval. Atripla stands to simplify dosing schedules and increase viral suppression of an affliction that affects more than 36 million people worldwide.

A recurring topic that will be addressed in the 21st century is the need for renewable energy sources. Wind, solar, natural gas, nuclear, and alcohol-based fuels will all be considered in coming years, and companies both large (like Applied Materials (NASDAQ:AMAT) and Air Products & Chemicals (NYSE:APD)) and small (like American Superconductor (NASDAQ:AMSC)) will all be seeking profits in this area.

Clearly, whatever combination of energies is ultimately implemented, a lot of money will be spent to meet our world's growing energy needs. At our Motley Fool Rule Breakers growth-investing service, one company we've recommended is Suntech Power, a Chinese business that designs, manufactures, and sells photovoltaic cells used to generate power in solar panels. Currently, solar power accounts for a small percentage of energy use, so there's huge growth potential here. Moreover, because Suntech is aiming to be the world's low-cost producer of solar technology, our team thinks the company is in a good position to meet both consumer and environmental demands.

How to profit from change
More world-changing technology will emerge in the 21st century than in any previous one. The Cato Institute's report noted that "the progress of the 20th century is not a mere historical blip but rather the start of a long-term trend of improved life on earth." Indeed, science and engineering have already reshaped the world we knew just 10 years ago.

This is great news for investors, especially with a lot of beaten-down innovators in today's market. Such innovation presents unparalleled opportunities to capitalize on the pioneering companies that will change our world -- but which of these companies is worthy of your investing dollars?

Fool co-founder David Gardner and his Rule Breakers team are always keeping their eye out for groundbreaking companies that also happen to have great business models. For example, in April 2005, the team noticed Intuitive Surgical's tremendous sales growth and its near-monopoly on the robotic technology that enables minimally invasive surgery. The pick has returned 204% for subscribers since then.

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This article was originally published Oct. 16, 2006. It has been updated.

Todd Wenning does not own shares of any company mentioned. Suntech Power Holdings and Intuitive Surgical are Rule Breakers recommendations. Garmin is a Motley Fool Global Gains pick. eBay is a Motley Fool Inside Value recommendation. Garmin and eBay are Motley Fool Stock Advisor picks. The Motley Fool is investors writing for investors.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.