I am a gas, an invisible traveler, moving freely in every space. You cannot see me, but you can feel me when the wind blows. When I am trapped inside a balloon, I make it float and expand. When heated, I become restless, spreading faster and pushing outwards. When cooled, I slow down and shrink. Without me, you cannot breathe because I am part of the air that keeps life alive. I am a gas, a quiet but powerful force of nature.