Abstract The hydroformylation or oxo‐synthesis is one of the most important transition metal assisted homogeneous catalytic transformation, providing industrial‐scale production of aldehydes and alcohols. The hydroformylation—homogeneous article presents the basic chemistry and kinetics of hydroformylation, solvents of hydroformlylation, and side reactions accompanying hydroformylation. The detailed reaction mechanisms related to the cobalt‐ and rhodium‐modified and unmodified catalysts are presented as well. The chemistry of the individual steps of the classic catalytic cycle based on results of model reactions and spectroscopic investigations is discussed and is followed by an overview of different catalyst modifiers such as phosphine and phosphite ligands.