A thirst crow came upon a pitcher that was half full of cool,clear water. The crow tried to take a drink, but his beak was not long enough. He tried over and over again, and was about to give up in despair when he hit upon a plan. One by one, he began dropping pebbles into the pitcher. With each pebble the water rose a little higher until at last it reached the brim, and the clever bird quenched his thirst.

Necessity is the mother of invention.