the.com/leaven
The quiet agent that makes dough rise and dull things suddenly worth eating.
means A substance like yeast that ferments dough and makes it puff up, or anything that subtly transforms a larger whole.
from From Latin levare, to raise or lighten — the same root that lifts elevators and relieves your burdens.
Biblical exilePassover bread skips it to honor a hasty escape.
Living thingSourdough leaven is a colony of wild yeast and bacteria.
Figurative useA leaven of humor can rescue a grim speech.