Sad Sad Superman

Having mentioned Superman's sad expression on that old comic book cover, I am reminded of the time he said, "'HEART OF STEEL' -- HUH? THEN -- WHY AREN'T THESE TEARS METAL? WHY DO THEY BURN SO?" and also the time that Jimmy Olsen provoked Superman until he burst into tears then collected his tears in a vial for reasons known only to Jimmy Olsen.