The nucleoside thymidine is formed from the combination of the organic base thymine and the sugar deoxyribose. Thymine was first isolated in 1893, before any other pyrimidines, and its structure had been determined by the dawn of the twentieth century. When phosphorylated with phosphoric acid groups, thymidine may generate three different nucleotides, thymidine monophosphate (TMP), thymidine diphosphate (TDP), and thymidine triphosphate (TTP). Though not particularly active as coenzymes, some of the thymidine-based nucleotides may readily donate atoms or groups of atoms to aid in the formation of more significant molecules, such as adenosine triphosphate (ATP). The molecule thymidine is itself important because of its role in DNA synthesis and genetic transmission.