So small that a trillion of them can fit in a drop of water, a biomolecular computer made of DNA detected cancer in a test tube and released a molecule to destroy it.

This was achieved with a 2004 version of the miniscule computer. The first version of the device was invented eight years ago by Prof. Ehud Shapiro and his team at the Weizmann Institute of Science’s biological chemistry department. It was the first autonomous programmable DNA computing device.

Shapiro’s team has just published an article about its advanced program that enables biomolecular computers to “think,” in the online edition of Nature and Nanotechnology.

The train of deduction that is the basis for the program was first proposed by Aristotle over 2000 years ago as a simple if/then (rule/fact) proposition: “All men are mortal. Socrates is a man. Therefore, Socrates is mortal.”

The team set up more complicated queries involving multiple rules and facts, and the DNA computing device was able to deduce the correct answers every time.