WORLD'S SMALLEST HARDEST

▶ Across

1. Curve-cutting line (abbr) (3) 4. Molecule part (4) 6. Knee-like structure (4) 7. Type of charge (abbr) (3)

▶ Down

1. Yield to gravity (3) 2. A giant (archaic) (4) 3. Eye receptor cell (4) 5. The face (inf) (3)