Laser is the 20th century after nuclear power, computer, semiconductor, human's another major invention, known as "the fastest knife", "the most accurate ruler", "the brightest light". The atom is called "laser" because of the radiation of light.

As electrons in an atom absorb energy, they jump from low energy levels to high energy levels, and from high energy levels to low energy levels. Lasers, on the other hand, are the queues of photons that are induced, and the photons in the queues of photons have the same optical properties and are in perfect alignment. For example, ordinary light sources, such as light bulbs, emit different photons, and will run in different directions, very disunited, but the photons in the laser are to think in one place, to work in the other, which leads to their invincibility and power.