Linear polyenes are an essential unit of studies of photoisomerization. Their relatively straightforward molecular structure, potential for electrical conductivity, and role in vision make them even more important. However, the simplest, 1,3-butadiene, has puzzled chemists for decades because of its complex excited-state electronic structure and its ultrafast dynamics. It is, in some ways, the "missing link" between ethylene with its single double bond, and the longer linear polyenes that have three or more. Now, an experimental team headed by Albert Stolow at the University of Ottawa and the National Research Council of Canada has solved the dynamic problem filling in the details between the single bond ethylene and the three-or-more polyenes.