The Reunion theory is often put into practice and proved with the ShinRa Underground's recycling program. When the clones get very far or we are low on clones within the facilities of the ShinRa Underground, we initiate a sort of miniature reunion. Using what is believed to be a small piece of the original body of Sephiroth, possibly excavated from the Icicle region, we place it in an accessible spot. As the clones return, we secure the area and commence in recycling.
The original Reunion theory was hypothesised by Professor Hojo and claimed that since Sephiroth was a nearer-to-human extension of JENOVA, that any clones deriving from JENOVA cells would be drawn to his spot to commence the reunion, which is believed to be a re-coalescing of JENOVA and its parts.