A method for obtaining crystals from a mother solution operates such that mother solution is fed into a crystallisation device. Supersaturation of the mother solution is brought about by open and/or closed-loop control of the temperature (). Seed crystals are added to the mother solution at a seeding point (Sp). The seed crystals are grown as nuclei by continuous closed-loop process control and are finally removed from the method as crystals. They form the product yield. The formation of crystal nuclei in the mother solution is countered by steps in the closed-loop process control. During the closed-loop process control and the crystallisation procedure, the position of the limit (M) of the formation of secondary nuclei is determined using sensors that detect data currently, wherein the position of the limit (M) is established as a value of the concentration (c) and the temperature () from these data. This determined position of the limit (M) of the formation of crystal nuclei is used as the basis for the closed-loop process control of the crystallisation.