The Rossmann fold is one of the most common and widely distributed super-secondary structures. It is composed of a series of alternating beta strand (ß) and alpha helical (a) segments wherein the ß-strands are hydrogen bonded forming a ß-sheet. The initial beta-alpha-beta (ßaß) fold is the most conserved segment of Rossmann folds. As this segment is in contact with the ADP portion of dinucleotides such as FAD, NAD, and NADP it is also called as an "ADP-binding ßaß fold". The Proteopedia entry on the Rossmann fold (Available at: http://proteopedia.org/w/Rossmann_fold) was generated to illustrate several structural aspects of super families of FAD and NAD(P) binding proteins: (1) The coenzymes FAD and NAD(P) share the basic adenosine diphosphate (ADP) structure. (2) The ßaß fold motif that is common to both FAD and NAD(P) binding enzymes accommodates the common ADP component of these two coenzymes. (3) In both FAD and NAD(P) binding sites, the tight turn between the first ß-strand and the a-helix is in contact with the two phosphate groups of ADP. (4) This hairpin curve includes the first two conserved glycines (Gly-x-Gly) that allow the sharp turn of the polypeptide backbone. (5) The two ß-strands of the ßaß fold may constitute the core of a larger ß-sheet that may include up to seven ß-strands generally in parallel orientation. (6) The structures of segments between additional strands vary greatly and may be composed of a variety of structures such as multiple short helices or coils.