Exponential assembly is a theoretical nanofactory process patented by Zyvex.
It is called exponential assembly due to the exponential growth of replicators which will construct themselves through self-replication. Thus, in geometric progression, one becomes two, then two becomes four, and so on.
K. Eric Drexler emphasised the inherent exponential nature of the growth of any replicator based on molecular nanotechnology in Engines of Creation (Chapter 10, Limits to Growth), and coined the word assemblers.