Google has released RAISR (Rapid and Accurate Image Super-Resolution) a software that can increase a photo resolution.
Applications like Photoshop have features to up-sample photos, thus increasing the number of pixel. What they do is to analyse the existing pixels and "stretch" them by including extra pixels that are a reasonable compromise between two nearby pixels. This is providing you with a virtually higher resolution photo, but the algorithm applied works only if the real object that has been photographed actually had a linear gradient of pixels. In many situations this is acceptable.
On the other hand RAISR is based on machine learning software. The software learns as it processes more and more photos. As an example it learns that a certain area is the image of human skin, another of human hair and based on that and on knowing how a high resolution skin, or hair, looks like it creates new pixels to actually increase the resolution by adding details (see the image) that "make sense".
Of course, the fact that the details added by increasing the resolution "make sense" does not mean that they correspond to the original. However, from the point of view of us, looking at a picture, the photo looks much better!
Amazing to see Artificial Intelligence carving a space into the Digital Darkroom!