Nolla in 1952 described the various stages of tooth development which are as follows: Stage 0 - Absence of crypt Stage 1 - Presence of crypt Stage 2 - Initial calcification Stage 3 - 1/3rd of crown completed Stage 4 - 2/3rd of crown completed Stage 5 - Crown almost completed Stage 6 - Crown completed Stage 7 - 1/3rd of root completed Stage 8 - 2/3rd of root completed Stage 9 - Root completed, apex open Stage 10 - Apical end of root completed, apical foramen closed Nolla's stages of Tooth Development