Prof. Jiří Křeček and his collaborators (eg. Hahn, Illnerová, Koldovský) have contributed to the development of the theory of critical developmental periods. His work of the consequences of early weaning for further development of the individual. There was formed a pilot study on the ontogeny of blood pressure and factors that affect it during development (Albrecht, Jelinek) in his laboratory. He was the outstanding representative of Czech post-war developmental  medicine based by Edward Babák.