Remembrance tanks allowed the Remote to reproduce. A quantity of biomass would be placed in the remembrance tank and a headset would be attached. Citizens would come and literally "remember" the person into existence. How a person was "remembered" depended on the impressions that the person had imparted to the society. It was felt that this method allowed for more variety than the more straightforward method of cloning, which would simply recreate the previous individual, where remembrance tanks allowed the new version to change and grow. During his time with the Eighth Doctor, Fitz Kreiner was captured and recruited by the Remote and a version of him was remembered into existence as Kode, but even after two centuries since the original Fitz was present Kode retained enough of Fitz's body language and mannerisms for the Doctor to recognise him, allowing him to use a remembrance tank and the TARDIS's own "memories" of Fitz to recreate Kode as Fitz. (PROSE: Interference - Book One, Interference - Book Two)
Faction Paradox used Gallifreyan biomass to remember Greyjan the Sane into existence. (PROSE: The Ancestor Cell)
In the City of the Saved, the Catholic Church had access to remembrance tanks. Father Tim Connolly used the tanks to create several Piltdown Men. (PROSE: The Adventure of the Piltdown Prelate)