What does it take to become a star? In the fall of 1948, Marilyn Monroe had just a few roles in box office flops on her resume -- but LIFE photographer J. R. Eyerman apparently saw enough of a glimmer in the 22-year-old starlet to follow her through the showbiz training that promised to make her big. The incredible -- and seldom seen -- images in this gallery are the first a LIFE photographer ever took of Monroe, though the magazine did not publish them at the time. (In fact, she wouldn't show up in LIFE's pages until October 1949, along with seven other then-unfamiliar Hollywood "girls"). But now, in celebration of what would have been Monroe's 85th birthday (June 1, 2011), LIFE.com presents these rare gems, restored to their original glory and showing early-career Monroe in the dance, acting, and voice classes that helped make her an icon for the ages. Here: Marilyn runs a hand through her long curls -- dyed but not yet that famous platinum hue -- in one of Eyerman's portraits.
Dancer in Training Of this photograph McKinney wrote, "She assumes the classic, much-painted posture of ballet girls adjusting their shoes." Around the time of Eyerman's shoot, Monroe was signed with Columbia Pictures, after a brief and unsuccessful six months at 20th Century Fox, and could be seen on screen as a dancer in Ladies of the Chorus. Ultimately, that movie tanked, and Monroe was once again dumped by a major studio -- but she would continue undeterred in her quest for fame.
Bosom to All the World' "Marilyn strains, back against the mirror, bosom to all the world, in an attempt to get a mood of elation."
Oh, the Drama! "We start the scene, student outdoing teacher in the clasped hands department and vice versa."
At the Mike Moore urged Monroe to get the most out of every line. "Get it in your head and sing it out. Believe it!" he told her, according to LIFE's notes.
'Her Own Little Voice' "Another phase of Moore's coaching: play-back recordings, to test the actual vocal technique. Marilyn seems fairly pleased by her own little voice; Moore is a little more dubious." Click here for the full collection of rare Marilyn Monroe photos from LIFE.com