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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for Microscopic bit:

ATOM: Microscopic bit
NANOPARTICLE: Microscopic bit
GENE: Microscopic bit of heredity
GUACAMOLECULE: Burrowing mammal's microscopic bit of party dip?
COVERSLIP: Bit of glass on a microscope slide