Photosynthesis begins with exposure to the sun's rays. Without the sun's rays, there would be no green plants, since the sun is an essential part of photosynthesis. Exposure to the sun's rays allows the chemical processes that drive plant food production to occur.

Absorbing the sun's rays is the function of chlorophyll, which can be found in the leaf's chloroplasts, which are small organelles in the leaves of plants. In turn, the chloroplasts, are responsible for taking in the energy from the sun and converting it to sugar that can be used as plant food.

Water that has been absorbed through the root system travels through the plant and to the leaves. Chloroplasts destroy the integrity of the water molecule by splitting it into hydrogen and oxygen. Once these two atoms are free, hydrogen can be accessed to combine with carbon and produce sugar or plant food.

Sugar is transported throughout the plant by special transport cells called phloem. The phloem provides the sugar to the leaves and entire stem so that the energy, stored in the sugar can be used.

The oxygen remaining from the split water molecule is released into the atmosphere. The release of oxygen, as a by product of photosynthesis, helps provide other plants and animals with a renewable oxygen source. That is why the air is cleaner in rural areas, compared to urban areas.