When an apple tree takes up water from the soil, it moves up through the roots, stems, and into the leaves. In the leaves, water is combined with carbon dioxide during photosynthesis to create glucose (sugar) and oxygen. Through transpiration, water is released from the leaves back into the atmosphere. This water vapor can then rise and eventually form clouds through a process called condensation, in which the water vapor cools and changes into liquid droplets or ice crystals. When the clouds become heavy with moisture, precipitation occurs, such as rain or snow, and the water droplets or ice crystals fall back to Earth. Therefore, a water molecule from an apple can eventually end up in a cloud and back to Earth through the natural water cycle.