AbstractThe chemistry of fuel‐rich hydrocarbon flames is extremely complex because different types of high molecular mass structures are produced. In fact, Polycyclic Aromatic Hydrocarbons (PAH) and submicronic turbostratic graphitic‐like particles (soot) are not the only products present but also partially aromatic polymers, gums, fullerenes and diamond‐like particles may be formed during pyrolysis and rich combustion. In addition, the heavy fractions of liquid fuels like the asphaltenes or the large polar‐aromatic compounds pyrolyze to specific forms of solid carbon. The tight requirement of a high space‐time resolution of the measurements during the high temperature combustion privileges the optical and spectroscopic diagnostics. This contribution will shortly review the main optical effects employed in this field namely absorption and fluorescence spectroscopy and elastic light scattering.