The T.I.E. starfighter was the first fighter to utilize the famous "ball-shaped cockpit flanked by vertical wings" design, and seemed very similar in terms of shape to its descendants.
The T.I.E. could be traced back to a courier design produced by Raith Sienar's Sienar Design Systems before 32 BBY, the ship which became Darth Maul's Scimitar—although Scimitar was a large, sophisticated runner rather than a compact, mass-produced starfighter. The next stage was the Advanced Project ship, a starfighter prototype design, the latest and smallest of which Sienar was building in 29 BBY.
It would be another seven years, however, before Sienar revealed the final component of the T.I.E. design, the SIE-TIE twin ion engine, a powerful and highly-innovative propulsion unit which was officially endorsed by Republic Sienar Systems shortly before the First Battle of Geonosis and the outbreak of the Clone Wars. This paved the way for the final starfighter design, and it meant that Republic Sienar Systems was well-prepared when the Republic called for a new, standard mass-production starfighter during the Clone Wars.
The T.I.E. production went underway as part of a drive by the Republic Navy to standardize their starfighter capability and create fighters that could deploy in the limited space available aboard existing warships like the Dreadnaught-class and Carrack-class cruisers.
Although the new engine design was incompatible with established hyperdrive, life-support and shield systems, the T.I.E. was incredibly cheap, very fast, and could stack tightly in converted cargo holds or external launch-racks aboard the Navy's existing line-combat ships. By the first weeks of the New Order, T.I.E. fighters, already known to front-line personnel as "TIE fighters", were deployed aboard ships, such as the Victory-class Star Destroyer Strikefast.
By this time, the original T.I.E. had evolved into the TIE starfighter, which would later be supplanted by the TIE/LN starfighter, the dominant starfighter model of the Galactic Empire.