The most significant experimental data on the formation of the common rhythm of the heart sinoatrial node are presented for both the intact heart sinoatrial node and cardiomyocytes in cell structures. The basic mathematical models for studying the synchronization processes in the sinoatrial node, including the Noble equation, Bonhoffer-van der Pol model, and modified axiomatic models, are described. The basic results obtained with the mathematical models are presented. The most important causes affecting the formation of the common rhythm—the pacemaker potential shape in the slow diastolic depolarization phase, its porosity, the coupling force between pacemakers, and the electrical power of pacemakers—are revealed. Rhythmogenesis is studied using the modified axiomatic model. The method allows the calculation of the common rhythm of the sinoatrial node, with allowance for the mutual effect of the pacemaker cells, including the coupling force, electric power of cells, and possibility of the cells clustering. It has been shown that the common rhythm of the sinoatrial node is generally formed at the intermediate level of the rhythms of all pacemaker cells.