This article is part of our Innovation in America series, in which Foolish writers highlight examples of innovation going on today and what they see coming in the future.

The keyboard and mouse are so last millennium.

Since the dawn of the PC decades ago, input has been traditionally handled by the good old keyboard and mouse. To be sure, they're likely not going anywhere anytime soon as a mainstay for interacting with technology. Rather, the real innovation in recent years is the evolution of input to include more natural interface methods that will define how the next generation of consumers will communicate with their machines.

Your kids will grow up in a world where they can get results by touching, talking to, and gesturing at their devices.

Can you feel it?
Touchscreen technology is nothing new, but it has evolved tremendously over the past five years. One of the early implementations of touch interfaces was a resistive touchscreen, invented in 1982 by Elo Touch Systems. Resistive touch acts very much like physical buttons built into a screen, where the user must physically press down on the screen for anything to be registered.

Resistive touchscreens are built with two conductive surfaces separated by air. When an object such as a finger presses the surfaces together to make contact, input is registered.

Apple's (Nasdaq: AAPL) original Newton Message Pad, introduced in 1993, used this technology, although the first device to be considered a commercially successful PDA was Palm's Palm Pilot 1000, which was introduced three years later, also featuring a resistive touch screen.

For the majority of their history, touchscreens have been dominated by the resistive flavor, representing 91% of unit sales as recently as 2007.

Nowadays, most touchscreens use capacitive touch, which is also not new. 3M (NYSE: MMM) patented capacitive technology as early as 1979. MicroTouch introduced the first capacitive touch sensor in 1995 and was subsequently acquired by 3M five years later. FingerWorks was a maker of various touch peripherals like keyboards and was later acquired by Apple.

The method involves a conductive coating applied to a screen with voltage applied to it that produces a uniform electric field across it. When you touch it with your finger, your body's natural electrical energy causes a disturbance and the electrodes that surround the screen can detect the new charge distribution in order to determine the positioning. These are now favored because input doesn't rely on physical presses; a gentle touch is sufficient and more intuitive for most users.

Touchscreens found in devices today use a more complex version of this technology, with screens comprised of hundreds of small independent electrode grids that facilitate more complex interactions with multiple fingers, known as "multitouch."

The vast majority of mobile devices today, primarily smartphones and tablets, feature capacitive touchscreens. More importantly, modern operating systems from Apple, Google (Nasdaq: GOOG), and Microsoft (Nasdaq: MSFT) are now optimized for touch input, the lack of which was largely why the first tablet PC movement a decade ago fell flat.

Instead of simply using touch instead of a mouse on a traditional desktop built for mice, software makers develop their interfaces specifically around touch input, which is cruder and less precise than mouse clicks due to the size of a person's finger.

iOS, Android, and Windows Phone all rely heavily on touch as the primary input method, using virtual onscreen keyboards when necessary. On traditional PCs, touch interactions usually take place through a trackpad.

Can you hear me now?
Voice is another aspect of how input is changing. The voice recognition industry is segmented between recognition and interpretation. Nuance Communications (Nasdaq: NUAN) leads the way in recognition software, while interpretation software can come in a wide variety of flavors and quality. Nuance also provides interpretation software, but that space is much more crowded than the recognition side.

Apple's Siri has played a large role in catalyzing other companies to fully embrace voice input, and adoption is just now beginning. One of the main things holding back voice recognition over the years has been a poor user experience caused by low-quality interpretation software lacking the intelligence to register the numerous ways a person can say something.

As the shift to natural language interpretation intensifies and software makers focus on intelligent interpretation, voice recognition is here to stay this time.

Can you see me now?
Microsoft is leading the way with gesture-based input, starting with Xbox Kinect. The company continues to invest heavily in its camera software technology in order to recognize physical gestures and movements, and Windows 8 will also feature gesture controls.

In 2007, Bill Gates and Steve Jobs did a historic joint interview at All Things D's D5 conference; here's an excerpt from an exchange with Walt Mossberg:

Mossberg: But, you know, you have the mouse, you have the icons, you move around, you have the -- I mean, and you talked about what a big gamble it was in '84 to do that and then the follow on with Windows. We still essentially have that approach and I'm just wondering is that going to change.

Gates: Touch, ink, speech, vision, those things come in, but they don't come in as a radical substitute. I think you're also underestimating the degree of evolution. ... You know, but there has been good evolution, but these natural interface things are the revolutionary change and they will be very revolutionary.

Are we there yet?
How often have you seen a futuristic sci-fi flick where a character interacts with technology using a three-dimensional touch interface that's manipulated by hand gestures while talking naturally to the computer?

We may not be there quite yet, but it's easy to visualize it on the horizon. The future will be here before you know it.

There's another technological revolution happening right now right here in America and it promises to forever change the way consumer products are manufactured. Grab this free video report to learn more about the next big thing in technology.

Read more about innovation today and its future in America; head back to the series intro for links to the entire series.