You are hiking on a trail through Yellowstone National Park. You are surrounded by many wonders of nature. You see tall, green trees, giant waterfalls, and geysers spraying water into the air. You hear birds chirping, the wind whispering in the leaves, and water gurgling in nearby streams. Maybe you even see a bison in the distance.

Suddenly you come to a clearing. Your eyes are drawn to a cloud of steam rising from the ground. You get a little loser, but not too close. You stop to look carefully. The mist appears to be coming from a big, beautiful pool of water. But this is no ordinary pool of blue water. This water has many colors. It looks like a rainbow. You are mesmerized by its rings of red, orange, and yellow, and the deep, rich blue at its center. Do you also see some green? You can't believe it's real. What is that?