Light, the first thing as human beings open eyes, is so important to everyone of us. It is also the most mysterious in the universe about which we have seemingly known a lot, but in fact we still know very little. From Isaac Newton's particle theory to Christiaan Huygens' wave theory then Albert Einstein's wave-particle duality, no one has ever told us what the particle is and how it waves. Here I show that the particle is paired electrons. The paired electrons spin in opposite directions moving in a harmonic oscillation close to each other by the attraction of electromagnetic field and spin angular momentum and in the meantime move in a forward circle with each other as the center. As they are nearest to each other, the repellence of electric field separates them and they move at a fastest centripetal speed. The centripetal speed is always greater than c. The greater the centripetal speed, the waving frequency of light. This is the brightest picture of light ever. This new picture of light can explain or can be evidenced by photoelectric effect, polarization, Wien displacement law, Compton Effect Zeeman's effect and optical activity, etc. Almost everything that relates to light can be explained by this “waving paired electrons” theory.