Early in the 1888, people had found liquid crystal's existence, it is almost transparent, it has the liquid and solid feature at the same time. And now, as a great progress, lad ad display and related products have been manufactured. See from the shape & look, it is a kind of liquid, but it's crystal type molecular structure has the solid form. Like the metal in the magnetic field, if it is influenced by the external electric field, the molecular will arrange orderly. If we do some appropriate control to the molecular, the liquid crystal molecules would let light to penetrate, the way light penetrate molecular can be decided by the molecules arrangement, this is also a kind of feature of solid.