The formation of atoms and radicals in the flame in concentrations by many orders of magnitude higher than the equilibrium values at combustion temperatures is explained. Results that prove the important role of homogeneous and heterogeneous reactions between atoms and radicals in combustion are presented. The decisive role of previously unknown reactions of heterogeneous chain propagation in combustion is illustrated by experimental results. The reasons for the misconceptions of several foreign and Russian authors who tried to deny chain combustion are explained.