Meaning: When people smile, their happiness grows and sadness disappears.
Choice of Words: Smiles are expressions of happiness or joy. Bloom means to open up or blossom, like a flower. Tears are drops of salty liquid that fall from the eyes when someone is sad or crying. Retreat means to move back or withdraw from a place or situation. When you put them together, the sentence suggests that happiness is spreading and becoming more visible, while sadness is fading away.