Scientists at the University of California, Berkeley found that by looking at brain activity, they could get a fairly good picture of a human's visual experiences. The study is published in the current issue of Current Biology.
So how did they do that? They made people watch short video clips and then they measured brain activity using a functional magnetic resonance imaging (fMRI) machine and they were able to recreate the clip people we watching. Here's a video with the recreations on the right and the video people were actually watching on the left:
But don't worry this technology is still far from revealing your deepest, darkest thoughts. The Scientific American writes:
The team, led by Shinji Nishimoto and Jack Gallant, say that the technology is decades away from enabling people to read others' thoughts and intentions. It could become a powerful tool to communicate with people who cannot verbalize, such as stroke victim and coma patients.