WordNet sense 1 (of or relating to or used in microscopy):

microscopical

WordNet sense 2 (sharply exact or accurate or delimited):

precise

WordNet sense 3 (immeasurably small):

minute, minute

WordNet sense 4 (infinitely or immeasurably small):

infinitesimal

WordNet sense 5 (limited or below average in number or quantity or magnitude or extent):

little