Matrix Soong was discovered and activated by his creator's (father's) best friend Geordi La Forge, shortly after Data's death during the USS Enterprise-E's mission to Romulus. He was the second Android created by Data, his older sister Lal died shortly after activation. Matrix was kept a secret by Data, since Lal's death was caused by a system-wide cascade failure, due to her positronic networks grew to the point where Lal could experiance emotions, occured pre-maturly. At the time There was a heated custody battle between Data and the Daystrom Institute. Where Admiral Haftel attempted to order Data to release custody of Lal.
Matrix entered Starfleet Academy shortly after. He made friends with Krothos a Klingon, Survic a Vulcan with emotions, and Tek'vrel the first Hirogen to enter Starfleet Academy. After he Graduated at the top of his class, Matrix was awarded rank of Lieutenant, and made Chief Medical Officer of the USS Dakota, a Nebula Class Warship in the Borg Defence Force. He was reassigned to USS Blade as Acting Chief Medical Officer until Dr. Paula Lins, the new Chief Medical Officer arrived. She asked him to stay as her Medical Adviser and he agreed.