Light, or Visible Light, commonly refers to electromagnetic radiation that can be detected by the human eye. Light can also be described in terms of a stream of photons, massless packets of energy, each travelling with wavelike properties at the speed of light. The term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The absorbed energy of the EM waves is called a photon and represents the quanta of light. Light is the primary source of energy for all living organisms. Plants, main sustainers of life, are crucial in this conversion process and need sunlight for photosynthesis that enables them to make their own food and food for others. And, perhaps more importantly, photosynthesis produces oxygen too!