Where does hunger originate?

hypothalamus

Explanation: The body's system for regulating food intake is coordinated by the hypothalamus, which is located under the midline of the brain, behind the eyes: Within the hypothalamus are nerve cells that, when activated, produce the sensation of hunger.

In the stomach.

Explanation:

In stomach where electrical (vagus nerve) signals relate the state of emptiness or fullness.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.