Why: Lithium-ion batteries make electric cars possible at mass-market prices.
Key innovation: Nanostructured electrodes result in lithium batteries more durable and safer than those in cell phones and laptops.
Why: The exponential growth in traffic on the Web is possible because of services that route data intelligently.
Key innovation: Its algorithms optimize online routes for content delivery.
Why: E-books are finally becoming a large, mainstream market.
Key innovation: Even as it seeded the e-book market with the Kindle, Amazon has made it easy for people to read e-books on other devices, such as the iPad.
Why: Smart electrical grids and more efficient power cables can help save money and energy.
Key innovation: Underground superconductor power cables using AMSC’s Amperium™ high temperature superconductor wire can carry up to 10 times as much electricity as conventional copper cables.
Why: Advanced biofuels could help reduce the use of gasoline and diesel.
Key innovation: Its genetically engineered yeast turns sugars into a building block of diesel fuel, which is usable in the existing transportation infrastructure.
Why: The rest of the consumer electronics industry is scrambling to catch up to the iPad. The iPhone still sets the standard for smart phones, even if its market share slips.
Key innovation: Its limited lineup of mobile devices all run on the same easy-to-use software.
Why: Powerful computing devices are proliferating because of chips that incorporate ever-smaller features without rising in price.
Key innovation: Its machines can make chips that have both vertical and horizontal connections, to pack in more computing power.
Why: It is redesigning smart phones and tablets so that they'll use much less power and need recharging less often.
Key innovation: Developed energy-efficient customizable chips for mobile devices.
Why: Many doctors and researchers lack the resources to sequence genomes and analyze them themselves.
Key innovation: Sells sequencing as a service, analyzing DNA samples that customers send in.
Why: New types of photovoltaics are reducing the cost of solar power.
Key innovation: "Thin-film" solar panels based on cadmium telluride, which are cheaper than conventional silicon panels, have made the company one of the world's largest photovoltaic manufacturers.
Why: Embryonic stem cells provide a potential source of replacement tissue for use in treating an array of degenerative diseases and injuries.
Key innovation: Has begun clinical trials for a spinal-cord therapy derived from these cells.
Why: Increasing the time that turbines are operational will lower the cost of wind power.
Key innovation: Co-developed a direct-drive wind turbine that eliminates the need for a gearbox. Having fewer moving parts reduces the chance of costly mechanical failure.
Why: It still sets the agenda in Web search, even as it pushes the development of Android for mobile devices.
Key innovation: Its software development process remains relatively fast even as the company has gotten very big.
Why: Smart phones that run Android have become an alternative to Apple's mobile devices.
Key innovation: Designed well-crafted devices in partnerships with Google and wireless carriers.
Why: Computing can transform infrastructure such as electric grids and traffic control systems.
Key innovation: Is drawing on its research expertise and that of software companies it's acquired to develop services for many infrastructure industries and expand the market for information technologies.
Why: Robots can save lives by doing jobs too dangerous for people.
Key innovation: Its small, agile robots can detect and dispose of explosive devices for the military.
Why: Quick, cheap DNA sequencing will lead to new diagnostic tests and targeted treatments.
Key innovation: Its desktop gene-sequencing machine costs $50,000, about a 10th as much as other machines.
Why: Inexpensive video on demand, delivered over the Internet, undercuts cable and points the way to a likely future for TV.
Key innovation: Built demand for a streaming video service by including it free with DVD-by-mail subscriptions.
Why: Mainstream use of electric cars could benefit the environment, especially where power is produced relatively cleanly.
Key innovation: Nissan's new electric car, the Leaf, has a reasonably modest sticker price of $32,000.
Why: Understanding molecular pathways of rare diseases can shed light on common ones.
Key innovation: Introduced the first medication for patients with benign brain tumors associated with a particular genetic disorder; now the drug is approved for treatment of kidney cancer and is in testing for other types.
Why: DNA sequencing provides a way to detect microbes in the environment and monitor the spread of viruses in our bodies.
Key innovation:Its sequencing machine can read single strands of DNA in real time.
Why: Drugs that target genetic mutations unique to cancer cells may be more effective than ones that act more broadly.
Key innovation: A new drug blocks the effects of a mutation thought to be present in as many as 8 percent of all cancers.
Why: Improving the electric grid is crucial to making alternative energy sources less expensive.
Key innovation: Developed wind turbines and other technologies for different aspects of the electric grid, from generation to transmission to distribution.
Why: Extremely large-scale production of solar panels is reducing the technology's cost.
Key innovation: Developed its own solar cells and equipment for manufacturing them cheaply.
Why: Hybrid cars can significantly reduce gasoline consumption by using an electric motor alongside a gasoline engine.
Key innovation: A market leader with its Prius model, it is developing battery technologies that are helping to make these cars less expensive and more energy-efficient.
Private Companies
Why: Targeting cancer drugs narrowly to tumor cells will improve efficacy and reduce the side effects of chemotherapy.
Key innovation: Its delivery system uses engineered nanoparticles to deliver drugs to specific cells.
Why: It efficiently produces solar thermal power, which focuses sunlight to heat water into steam.
Key innovation: A boiler is heated directly with sunlight that bounces off mirrors.
Why: Its technology can reduce the cost of computing in data centers.
Key innovation: Runs servers with cell-phone chips rather than processors built on industry--standard designs, which are more power-hungry.
Why: Screening drugs on human heart cells will help researchers find treatments for cardiac problems and test drugs for toxic side effects.
Key innovation: Uses induced pluripotent stem cells to make large numbers of heart cells for testing.
Why: Simple, fast diagnostic tests can help physicians track disease-related markers.
Key innovation: Its microfluidic device for doctors' offices can quickly detect elevated protein levels associated with prostate cancer.
Why: Web applications must get faster and feel much more responsive to users if cloud computing is to keep growing.
Key innovation: Its technology efficiently routes traffic across the Internet and makes websites faster.
Why: Corporate decision-making gets smarter if it taps the insights of rank-and-file employees.
Key innovation: Private prediction markets let employees forecast the results of corporate choices.
Why: Reducing the cost of constructing solar thermal plants will make them more competitive with fossil-fuel plants.
Key innovation: Software controls the mirrors that focus rays from the sun, eliminating the need to position them by hand.
Why: Social networking on the Web is becoming a powerful advertising medium and a platform for startups that offer add-on services.
Key innovation: Adapts quickly to shape its site into a medium that advertisers consistently want to use.
Why: By encouraging millions of people to sign up for quirky daily advertising e-mails, Groupon has created one of the fastest-growing revenue generators on the Web.
Key innovation: Offers local businesses a way to guarantee a return on their promotional budget, thereby tapping into a huge advertising pool that has eluded many Web companies.
Why: Biofuels could be far cheaper if they weren't made from corn, sugarcane, and other forms of biomass.
Key innovation: Designed microbes that convert carbon dioxide and water directly into fuels.
Why: Light-emitting diodes are an energy-efficient option for lighting in buildings and homes, but they are still expensive.
Key innovation: Its low-cost process produces LEDs on the same equipment used to make semiconductors.
Why: Augmented reality enhances the value of a mobile device, employing its camera and GPS and displaying information about the user's surroundings.
Key innovation: Its development platform lets businesses and advertisers add AR functions to their own apps.
Why: Computer chips that operate with probabilities instead of binary logic could speed applications such as fraud analysis and machine vision.
Key innovation: Its microprocessor uses electronic signals to represent probabilities rather than binary 0s and 1s.
Why: Biodegradable plastics that aren't made from petroleum offer several environmental benefits.
Key innovation: Its polymer-¬manufacturing processes use carbon dioxide to make plastics needed for packaging.
Why: User interfaces based on gesture recognition make possible new applications in gaming and everyday computing.
Key innovation: Developed the 3-D sensor system that Microsoft's Kinect device uses to track movement.
Why: Retrofitting existing buildings is a cost-effective way to increase energy efficiency.
Key innovation: Mass-produces windows with energy-saving features such as coatings and gas insulating layers.
Why: Computer intelligence in the electric grid will make energy distribution more efficient.
Key innovation: Developed hardware and software that standardize the way disparate parts of the grid communicate.
Why: Budget cuts will force NASA to rely on private companies for supply missions and other tasks.
Key innovation: Introduced a low-cost production method for everything from rocket engines to astronaut capsules.
Why: Expanding the use of mobile payments will help small businesses.
Key innovation: Built technology that lets anyone accept credit cards using smart phones.
Why: Genetically engineered microbes are a promising way to make biofuels.
Key innovation: Created synthetic bacterial cells, possibly paving the way for organisms specifically tailored to make fuels.
Why: Conventional solar power is still too expensive to compete with fossil fuels, in part because of the cost of manufacturing silicon-based solar cells.
Key innovation: Developed a cheaper method for making silicon wafers, the most expensive component of a solar module.
Why: Now that the company has begun to make money from its large user base, a service that has woven its way into everyday life is more likely to stick around.
Key innovation: Its business model offers selected opportunities for advertisers while drawing income from deals that let search engines index its content.
Why: Web tools can help people respond to crises such as earthquakes and political protests.
Key innovation: Its open-source crowdsourcing tool overlays field reports on maps, providing critical and often life-saving data during emergencies.
Why: Companies are building ¬businesses inside platforms like Facebook.
Key innovation: Its social games offer people a new way to interact online.
