In a cubic micron, you can construct the equivalent of a mainframe computer with a gigabyte of memory You have enough computational cycles within the volume, time, and heat-dissipation constraints to identify all the macromolecules of the cell (even if they're moderately damaged), by using certain algorithms that can already be specified in fairly great detail. Since you can identify all the molecules, you can map the cell structures: the patterns that you recognize are type-tagged by the molecules they contain (i.e. if it contains tubulin, it's a microtubule). Since this tells us the type of structure, it makes it easier to know how to probe and further characterize the structure.
This image shows the initiation of a cell repair sequence (cutaway view).
K. Eric Drexler, "Molecular Technology and Cell Repair Machines," paper presented at the 1985 Lake Tahoe Life Extension Festival, 25 May 1985; reprinted and published in Claustrophobia Magazine (August-October 1985) and in Cryonics Magazine (Dec 1985 - January 1986).