(A) Adenosine modifications resulting from conjugation to ubiquitous electrophilic metabolites. (B) Chemically sophisticated hypermodifications discovered throughout the past five decades. The year of publication is given in brackets. (C) C5-modified cytidines related to so call epigenetic DNA modifications recently discovered. m6A, 6-methyladenosine; ac6A, 6-acetyladenosine; t6A, 6-threonyladenosine; i6A, 6-isopentenyladenosine; Arp, 2’-O-ribosyladenosine phosphate; yW, wybutosine; oQ, epoxyqueuosine; tm5U, 5-taurinomethyluridine; nm5ges2U, 5-aminomethyl-2-geranyluridine; 5-methyluridine; ho5C, 5-hydroxycytidine; f5C, 5-formyluridine.