In 1974, a visiting researcher in Hideki Shirakawa's lab at the Tokyo Institute of Technology made a historic error: he added a Ziegler-Natta catalyst concentration roughly a thousand times higher than the polyacetylene synthesis recipe called for. Instead of Natta's black, intractable powder (1958), the result was a flexible, shiny, silver-colored plastic film: trans-polyacetylene. Though the material still did not conduct electricity well, this manipulable film form of the polymer was the physical object that for the first time allowed experimenting with its electrical properties. MacDiarmid and Heeger, upon seeing the film in 1976, invited Shirakawa to Philadelphia, where they conceived the doping experiment that in 1977 produced the first conductive plastic.