An interview with David Gordon Wilson of M.I.T. who talks of trial and error as a focused learning process; an interview with Paul MacCready, designer of a flying bicycle called the "Gossamer Condor," relates the process by which the final structure of the Condor was determined; Vincent J. Schaefer recounts his accidental discovery, in 1946, of a way to eliminate the supercooling of clouds which caused airplane wings to ice; a look at the Tour de France, where cyclists and designers continually experiment with ways to increase speed; a discussion of the work of German immunologist Paul Ehrlich, who, in 1901 discovered a cure for syphilis; a scientist who looks in the ocean for organisms, avoided by others, which may contain chemicals that fight disease; and another visit to the Human Powered Championship, including interviews with designers of unusual vehicles.