atomic
brownian
corpuscular
embryonic
evanescent
germinal
granular
impalpable
imperceptible
imponderable
inappreciable
indiscernible
infinitesimal
intangible
invisible
microcosmic
microscopic
subatomic
tenuous
thin
ultramicroscopic
unseeable
biochemical
biological
cellular
experimental
internal
linear
magnetic
organic
structural
visual
intermolecular
secular