Short answers, pulled from the story.
Google engineer Alexander Mordvintsev created the DeepDream software program in 2014. The project began as a deep convolutional network codenamed Inception after the film of the same name.
Google released the public version of the program in July 2015. Before this release, similar methods had been used to synthesize visual textures by other research groups.
The software uses a convolutional neural network to find and enhance patterns in images via algorithmic pareidolia. Applying gradient descent independently to each pixel produces images where adjacent pixels have little relation until regularizers are applied.
A study published in the journal Entropy in 2021 demonstrated the similarity between DeepDream and actual psychedelic experience. Researchers recorded Electroencephalography EEG of human participants during passive vision of a movie clip and its DeepDream-generated counterpart.
DeepDream was used for Foster the People's music video for the song Doing It for the Money. The software enabled users to apply the dream-like appearance to deliberately overprocessed images.