My research centers on conceptual innovation in scientific revolutions. It concentrates on the theoretical representational practices of scientists who have created major conceptual innovations in 19th and early 20th century physics. Certain heuristics have figured prominently in many instances of major conceptual innovation and change: (1) analogy, (2) imagery, and (3) thought experiment. Although they constitute a substantial portion of scientific method, none except analogy has received more than scant attention in the philosophical literature on scientific method. The main problem philosophers have had in countenancing these as methods are that they are non-algorithmic and, thus, even if used correctly, may lead to the wrong solution or to no solution. This very feature, however, makes them much more realistic from a historical point of view, where one needs to understand the constructive practices scientists use in their research irrespective of whether the scientists in question went down dead ends, contributed to "winning" science, or employed different strategies in making a "simultaneous discovery."