Water vapor is the gas form of water and is usually invisible unless temperature or changes in pressure cause it to condense. When condensation occurs, the invisible water vapor changes from a gas to tiny particles of liquid water suspended in the air. This results in clouds or the visible steam that can come out of your mouth. Your lungs are full of moist air, so making water vapor come out of your mouth is easily done by either using cold temperature or high pressure.

Method 1: Cold Air Method

In hot conditions or cold, when you breathe out, the air has water vapor. At room temperature and above, you can't normally see the vapor. When you exhale in chilly conditions, the invisible water vapor in your breath meets the cold outside air; as it does, the vapor suddenly cools. The microscopic droplets of water in the vapor combine with each other forming droplets that are larger (though still small) and can catch the light, becoming visible.

••• Adrián González de la Peña/Demand Media Stand in a location with very a low temperature. This can be outside in the winter or indoors in front of a freezer. ••• Adrián González de la Peña/Demand Media Take a deep breath and exhale slowly through your mouth. You should see a visible cloud generated by your mouth. ••• Adrián González de la Peña/Demand Media For a large cloud, exhale slowly with a wider mouth. Breathing out quickly will create a fainter cloud. Experiment to create the effect you prefer. ••• Adrián González de la Peña/Demand Media To see a longer lasting effect of the water vapor, breathe onto a piece of glass in the cold location. The cloud will condense and remain on the glass for a longer period of time than in the air.

Method 2: Mouth Pressure

Unlike solids or liquids, gases have the property of being easily compressible; you can squeeze the same amount of gas from a larger to a smaller container, provided you apply enough force. The strength of your lungs and diaphragm muscle is sufficient to compress the air in your mouth such that the droplets of water vapor collide with one another, condensing into a visible mist.