Cell phones are an integral part of our lives. We use them to stay in constant contact with family, work and friends. We swap text messages (SMS) in traffic. We send tweets from the street. Heck, we even surf the Internet in the bathroom.

That's why our cell phones are so painful to give up when we travel to places where they don't work. In the past it could be very difficult -- or at least very expensive -- to use your cell phone outside of your home network. But the times are changing.

For years, cell phone carriers in the United States relied on technologies that were incompatible with those used in Europe, Asia and much of the rest of the world. Recently, two major U.S. cellular carriers -- AT&T and T-Mobile -- built nationwide networks based on Global System for Mobile communication (GSM) technology, the international standard for cell phone networks.

Today's computer-animated movies do a pretty good job of imitating three-dimensional environments. In films like "The Incredibles," "Cars" and the "Shrek" series, characters seem to exist as solid objects that can move and interact with their surroundings. It takes a lot of work and a good understanding of how people perceive images to achieve this effect. Filmmakers even make real, tangible models of their characters, known as maquettes, to help them figure out how a 3-D character would move in a 3-D space.

In the past few years, filmmakers have taken this attempt to recreate three-dimensional space on screen one step further. With digital 3-D, animators can fool your eyes and brain into thinking that they're looking into a 3-D space rather than at a 2-D screen. The end result is like looking through a window into a real, three-dimensional world or like having elements of the scene in the theater with you. While it's similar to older 3-D movies, the technology is considerably more advanced.