Interesting topic, albeit somewhat off-topic for the list. (My apologies for continuing it... :-) Some disruptive technologies are subsets of others; e.g. transistors are in some sense a subset of electrical (altough, as Chuck points out, they also draw on materials science). And how far back do you want to go? The discovery of metals certainly had a huge impact, albeit that it was many thousands of years ago now! But among the big ones for me are electricity, which almost has too many subsets to count (e.g. long distance communication, starting with the telegraph - read "The Victorian Internet" for a good look at how that changed the world), the printing press (information technologies in general have outside weight, since they affect so many other fields), the internal combustion engine (which has physically re-shaped entire civilizations, especially the US), with all its subset (e.g. the airplane)... too many to think of, almost! And it all started with sharp stones... :-) I am somewhat ashamed to admit that before today, I had not (that I can recall) heard of him. And I see there is no full-length book on him. A hole waiting to be filled, as it were... Noel