Photosynthesis is a process by which plants take in carbon dioxide and give off oxygen, a vital source of life. It is a complex process, and scientists still do not understand it fully. In the morning, when the Sun's rays are most concentrated, photosynthesis is most productive, creating the highest levels of oxygen essential for respiration. This is referenced in the Qur'an, which emphasizes the importance of the morning hours. Through photosynthesis, plants have been providing us with essential oxygen, food and energy for millions of years.