Attempts to model the formation of the "first" star from the pure hydrogen and helium gas clouds below about 10,000 K show that the heat generated in the gravitational contraction phase must be somehow radiatively released for further cooling to be possible. This is no problem as long as temperatures are still high enough so that free electrons exist: electrons are efficient emitters when interacting with neutrals (bremsstrahlung). However, at the lower temperatures in neutral gases, the recombination of hydrogen atoms to H 2 molecules is a process that generates enormous amounts of heat that must somehow be radiated away in CIE processes; if CIE were non-existing, molecule formation could not take place and temperatures could not fall further. Only CIE processes permit further cooling, so that molecular hydrogen will accumulate. A dense, cool environment will thus develop so that a gravitational collapse and star formation can actually proceed.