A "feedback crystal" is a cellular automaton (similar to Conway's Game of Life) where the rules are represented by a randomized kernel. The kernel determines the micro and macro structures that develop in the crystal. The crystals are grown from "seed" pixels (in this artwork, the white outline and white center pixel provide the seed).
Sometimes the patterns are chaotic, sometimes they are stable. If you are lucky, a pattern will be generated "on the edge of chaos" that mixes stability and chaos in an emergent complex system. These are rare. In addition, a small number of artworks will result in "dead" crystals that do not grow. These are also rare, but there is a chance that your crystal will be a mostly black square.
Each piece is composed of 3 different randomly generated kernels that sweep outwards from the center.