atomic, behind the curtain, behind the scenes, camouflaged, concealed, corpuscular, covered, disguised, embryonic, evanescent, germinal, granular, hidden, impalpable, imperceptible, imponderable, inappreciable, indiscernible, infinitesimal, insensible, intangible, latent, masked, microcosmic, microscopic, molecular, out of sight, secret, sightless, subatomic, submerged, tenuous, thin, ultramicroscopic, unapparent, unappreciable, unbeheld, unbeholdable, undetected, undiscernible, undisclosed, undiscovered, undivulged, unexplained, unexplored, unexposed, unnoticed, unobservable, unobserved, unperceivable, unperceived, unrealized, unrevealed, unseeable, unseen, unsolved, unspied, untraced, untracked, unviewed, unwitnessed, veiled, viewless