Why is this the answer?

The answer is dew because this beautiful riddle paints a perfect picture of what you find outside on a summer morning before the sun gets too high. Dew is one of nature's little secrets that you can see only at the beginning of the day. The first wonderful clue is "A tiny bead." If you walk onto the grass very early, you will see it covered in countless little drops of water. Each drop is perfectly round and small, sitting right on the tips of the leaves, just like a miniature bead you might see on a bracelet. Dew is not rain; it is water that comes right out of the air. When the sun goes down, the grass and leaves get very cold. The warm air floating over the cold ground has water vapor in it, and when that vapor touches the cold grass, it cools down so much that it turns back into liquid water. These liquid drops are the tiny beads. Next, the riddle says the bead is "like fragile glass." The water drops are perfectly clear and shine so brightly when the light hits them, almost like they are tiny pieces of crystal. The word "fragile" means something is very easy to break, and these water drops are fragile too. They vanish quickly. As soon as the sun shines brightly and warms up the grass, the drops heat up and float back into the air as vapor. If you try to collect them or step on them, they pop and are gone. They are a temporary, beautiful decoration that you can only enjoy for a short while before they disappear. The last part of the riddle, "strung along a cord of grass," gives us the final location clue. A cord is like a thin rope or string, and the blades of grass look just like green strings across the lawn. The dew drops often line up one after another along the very edge of the grass blade. It truly looks like someone carefully strung the clear, round beads along a green cord. This clever description of a tiny, clear water drop on a blade of grass is exactly why the answer must be dew.