Most regular liquids feature molecules that tumble around randomly with no real order or pattern. Solid crystals have molecules that are locked firmly into a rigid, repeating three-dimensional grid. Liquid crystals exist in a strange, flexible middle ground between these two normal states of matter.
The smectic phase is considered one of the most highly organized forms of a liquid crystal. The molecules do not just point in the same direction, they also gather into clearly separated layers. You can think of these specific layers like flat sheets of paper sliding easily over one another.
Chemists classify different types of smectic phases depending on how the molecules sit inside their specific layer. In a smectic-A phase, the rod-shaped molecules stand perfectly straight up and down inside their layer. In a smectic-C phase, the molecules lean over and tilt at a sharp angle inside the layer.
Because of these stacked layers, smectic materials feel very thick, soapy, and slippery to the human touch. In fact, the word smectic actually comes from an ancient Greek word that translates to soap. These layered molecules respond very quickly when you apply a strong electrical charge to them. This makes them incredibly useful for building modern digital screens, smart windows, and electronic optical shutters.