Fractal neuronic cloning was a radical technique for creating an android with a stable positronic matrix, developed by Dr. Bruce Maddox and studied by Federation scientists in the late 24th century.
Relying on the prior existence of a neural network from an existing android, this technique posited that the complete code for a new android, even including memory, could be reconstituted from a single positronic neuron of the original. The approach also entailed the creation of identical twin androids as "children" of the "parent" android.
As described to retired Admiral Jean-Luc Picard by Dr. Agnes Jurati of the Daystrom Institute's Division of Advanced Synthetic Research, this approach could be used to create an android out of biological material – "out of flesh and blood" – appearing to be Human. Based on his recent encounters with Dahj Asha, Picard and Jurati speculated that Dahj was created through fractal neuronic cloning of a neuron from Data.
A symbol of two interlocking circles was a recognized symbol for fractal neuronic cloning; both Dahj and her twin, Soji Asha, possessed necklaces with this symbol. (PIC: "Remembrance")