X-Men The Hidden Years (I) (1-22) (1999-2001)
This series takes place between X-Men (I) #66 and #93.
Series	No.	Date	Year	Title
X-Men The Hidden Years	1	December	1999	Once more Savage Land
X-Men The Hidden Years	2	January	2000	The ghost and the darkness
X-Men The Hidden Years	3	February	2000	On wings of angels
X-Men The Hidden Years	4	March	2000	Escape to oblivion
X-Men The Hidden Years	5	April	2000	Riders on the storm
X-Men The Hidden Years	6	May	2000	Behold a goddess rising...!
X-Men The Hidden Years	7	June	2000	Power play
X-Men The Hidden Years	8	July	2000	Shadow on the stars
X-Men The Hidden Years	9	August	2000	Dark destiny
X-Men The Hidden Years	10	September	2000	Home is where the hurt is
X-Men The Hidden Years	11	October	2000	Destroy all mutants!
X-Men The Hidden Years	12	November	2000	And death alone shall know my name
X-Men The Hidden Years	13	December	2000	Blood and circuses
X-Men The Hidden Years	14	January	2001	Yet no more like my father...
X-Men The Hidden Years	15	February	2001	Death be not proud
X-Men The Hidden Years	16	March	2001	Echoes of a lost generation
X-Men The Hidden Years	17	April	2001	Hunter and hunted
X-Men The Hidden Years	18	May	2001	Promise of a new tomorrow
X-Men The Hidden Years	19	June	2001	Broken promises
X-Men The Hidden Years	20	July	2001	Worlds within worlds
X-Men The Hidden Years	22	September	2001	Friends and enemies