While they might be the most recognizable part of Star Wars, the technology behind lightsabers has never really been explained on screen. So, how do lightsabers work? Audiences may have picked up on the fact that kyber crystals were mentioned as the source of power for lightsabers in Rogue One, but only if they were paying close attention. It's certainly true that kyber crystals (otherwise known as lightsaber crystals or focusing crystals) are the most important part of building a lightsaber, but there's far more going on inside the hilt of one of these Star Wars weapons.
Lightsabers are intricate tapestries of electronics and Force power that take great skill to both build and use. Lightsaber designs are as varied as their wielders, but they all have similar components at their center. Jedi, Sith, and really every Force-user employs minor differences in the way they construct their weapons, but there's a standard process behind their creation and use. If you've ever been curious how a lightsaber works, you don't need to rely on the vauge riddles of tiny orange aliens with huge glasses. Here are the cold, hard, lightsaber-y facts.
By far, the most important part of a lightsaber is the focusing crystal. Also known as a kyber crystal, these minerals are Force-attuned and found on certain planets such as Jedha, Ilum, and Dantooine. These crystals not only help focus the Force into the blade, but they can also be used as important technological components. In the old Expanded Universe (now the Star Wars Legends), most crystals or gem could work in a lightsaber. However, in the current continuity lightsabers exclusively use kyber crystals.
While technically anyone can wield a lightsaber, building one is another matter entirely. In the new continuity, it's been established that Jedi crystal caves typically test Force-sensitive people with a trial. If they pass, they're rewarded with a kyber crystal.
Of course, as Rogue One proved, if you have the infrastructure you can just go right in and dig them up. Still, the actual construction of a lightsaber is incredibly complex. It's been shown that using the Force is incredibly helpful when putting one together.
Lightsabers are usually built with one main crystal, which produces a blade that's typically around meter in length. However, some Jedi (and Sith) seek an edge in length, so they build lightsabers with multiple crystals.
A dual-phase saber is a weapon with two to three crystals, and allows the user to adjust the length of the blade far beyond a meter. Some of the most famous Jedi and Sith in history used this type of saber, including Darth Vader.
If you're wondering why Kylo Ren's lightsaber has that unstable rippling effect, look no further than his kyber crystal. In his case, his cross guard saber has a cracked crystal, which makes the blade's energy unstable and unpredictable. The upside is that it can do more damage, but it can also short out or explode in the wielder's hands.
In fact, the two vents on the side of his saber are specifically designed to bleed excess energy off in order to keep the weapon more stable. There are other types of crystals, such as synthetic ones, that can carry other properties and create new blade effects.