Microscopic to us? I mean, we could, in theory, be microscopic organisms to some larger observer. But, in the case of single, microscopic cells (or microscopic multicellular organisms like rotifers) as we know them, I don't think it's possible for intelligence to exist at such scales. A body capable of supporting intelligence would require far more matter, energy, and organization, just as a book with more detailed information is typically larger than one without. To cram the physical necessities of intelligence into a space a few hundred microns cubed or less would be basically impossible (at least, from apparent indications. Ponerinecat, you can take your own opinion from this, as seems tradition on this thread)