New developments in molecular genetics, explaining over the past decade the changes in floral organ identity and distribution, are presented and discussed. Specific mutations of homeotic genes changing flower phenotype are described as factors leading to the outstanding diversity of floral patterns present in Angiosperms. Special attention is paid to the systems interacting with each other as well as acting independently. Aspects of meristic variation are underlined as important for the development of different floral symmetry in evolutionary lines of Monocots and Eudicots.