The Jedi Order originated in the Ossus solar system. This system was rich in Adegan crystals, which play a vital role in the creation of lightsaber blades. It became a vital strategic outpost in later years, when the Jedi order suffered the first of several great Schisms. Two great Jedi generals, Revan and Malak, were turned to the dark side. While they would later find a measure of redemption, their actions opened the door to the later Sith uprisings, leading to the Sith becoming disciples of the Dark Side of the Force and threats to the Jedi and the nascent Old Republic.
Lightsabers have been used by the Jedi Knights for thousands of years, and their design has remained essentially unchanged. They consist of a 10-inch-long metal handle lined with control studs. An Adegan crystal is mounted in its center. Once it's activated, the lightsaber channels energy through a lens at the center of the handle that projects it outwards to form one half of the blade. The energy then folds back on itself to complete the blade.
The first lightsaber seen in a Star Wars movie is the lightsaber Obi-Wan Kenobi gives to Luke Skywalker in "Star Wars Episode 4: A New Hope." This was Luke's father's lightsaber, and the scene serves as both a test and a passing of the torch, as Ben tells the young man a version of the truth about his father and his heroics during the Clone Wars. This sets Luke off on his quest to become a full Jedi Knight.
Several lightsaber variants have notable places in Star Wars history. The most obvious is the twin-bladed weapon wielded by Darth Maul in "Star Wars Episode 1: The Phantom Menace." It consisted of two lightsabers welded together hilt to hilt. Other notable variants include the curved lightsabers used by Asajj Ventress and the forked lightsaber used by General Roblio Darte during the Clone Wars.