DeepDream is, well, I can't improve upon Wikipedia's definition:
DeepDream is a computer vision program created by Google engineer Alexander Mordvintsev which uses a convolutional neural network to find and enhance patterns in images via algorithmic pareidolia, thus creating a dream-like hallucinogenic appearance in the deliberately over-processed images.
The freaky images took the web by storm a couple of years ago after Google open-sourced the code, allowing people to create their own DeepDreamed imagery.
In the video above, Mordvintsev showcases a DeepDream-ish new use for image generation via neural network: endlessly zooming into artworks to find different artworks hidden amongst the brushstrokes, creating a fractal of art history.
Bonus activity: after staring at the video for four minutes straight, look at something else and watch it spin and twist weirdly for a moment before your vision readjusts. (via prosthetic knowledge)