He played an instrumental role in the establishment of national rights for Romanians in Transylvania (part of the Habsburg monarchy at the time of his life).

He was born as Ioan Micu (Inocențiu being his clergy name, and Klein the German translation of his surname, sometimes rendered back into Romanian transcription as Clain) in Sadu, nowadays in Sibiu County, in 1692 from a lower-class family.

[1] On 18 November 1728, following the death of previous bishop Ioan Giurgiu Patachi, the electoral synod convened and Micu resulted the more voted, even if he was young and he had not yet terminated his studies.

Pope Clement XII confirmed him on 11 September 1730, and accordingly he was consecrated a bishop on 5 November 1730[2] by Gennadius Bizanczy,[3] the Eparch of Mukachevo.

As a member of the Diet (Parliament) of Transylvania, Inocențiu Micu began to press the Habsburg monarchy to fulfill the Agreement that conversion to Greek Catholicism would bring with it Roman Catholic-like privileges for Romanian inhabitants also, and an end to serfdom.