The size category Fine includes things 6" and smaller, but is there a point at which things are so little that they are no longer limited by the constraints of the size category Fine? That is, can a square hold only the same number of Fine creatures as Fine rocks, grains of sand, or even atoms?
Here's the plan: A psion wants to manifests the 9th-level psion/wilder power microcosm [telepathy] (Expanded Psionics Handbook 118) so as to secure as many creatures within the shared reality as possible. He wants to keep the affected creatures that share that reality alive and preserved in quintessence created by the 4th-level shaper power quintessence [metacreativity] (XPH 128), probably in a backpack or something. He also plans to visit that shared reality on occasion using, for example, the 4th-level oneiromancy spell dream walk [conj] (Heroes of Horror 129) or the 9th-level psion/wilder power reality revision [clairsentience] (XPH 128-9).
So were the creatures that are to be secured in the shared reality created by the power microcosm to manifest first the 4th-level power metamorphosis [psychometabolism] (XPH 116-7) to assume the forms of germs, grains of sand, or subatomic particles then reduced to 0 hp or less but not slain, would the psion be able to affect with the microcosm power more of these infinitesimally little creatures than he would have affected were the creatures either to possess the size category Fine naturally or to have manifested the metamorphosis power to assume the form of creatures of Fine size?
For example, can 2 billion of these grains-of-sand creatures be compacted into 2 cu. ft. so that they could all be affected by a lone manifestation of the power microcosm, slathered with quintessence, and stored in a typical backpack?