Computronium is a material hypothesized by Norman Margolus and Tommaso Toffoli of the Massachusetts Institute of Technology to be used as "programmable matter," a substrate for computer modeling of virtually any real object.
It also refers to a theoretical arrangement of matter that is the best possible form of computing device for that amount of matter.
Computronium in popular culture
In the Hitchhiker's Guide to the Galaxy books, by Douglas Adams, the entire Earth is portrayed as programmable matter; a computer designed to find the question to the Answer to Life, the Universe, and Everything.
In Orion's Arm Universe Project computronium is any form of matter which supports computation, including the human brain.
In The Turing Exception Singularity Series Book 4 by William Hertling Artificial Intelligence utilizes Nano Technology to create vast fields of solar powered computronium out of existing materials, on Earth during an attack on humanity. 
In Destiny (video game) the most common currency, Glimmer, is described as programmable matter that can be transmuted into nearly anything, similar to computronium.
In Hannu Rajaniemi's books "The Quantum Thief", "The Fractal Prince" and "The Causal Angel", planet-sized supercomputers are made of it.
- Amato, I. (21 Aug. 1991). Speculating in Precious Computronium. Science 253:856-857.
- CFAI glossary: computronium
- Zendegi, p. 72, at Google Books
- http://www.amazon.com/Turing-Exception-Singularity-Book-ebook/dp/B00UGIOCUK/ref=sr_1_3?s=digital-text&ie=UTF8&qid=1435678349&sr=1-3&keywords=william+Hertling | Loc 4430 of 4585 | text=...turning into a vast plain of glittering solar-powered computronium as it grew from dozens to hundreds of miles in diameter.