Kate Middleton shocked the world with a noticeable head scar.

Speculation about the scar led to rumors of brain surgery.

Reports revealed she had surgery during her school days.

A lump on her head was discovered at Marlborough school.

School informed Kate's mother, who rushed her to the hospital.

Emergency surgery removed the lump and left a scar.

Initial belief: scar from misplaced hair extensions.

Kensington Palace confirmed surgery in 2011 but didn't disclose the ailment.

Mystery still surrounds the exact reason for Kate's surgery.