This episode shifted the focus from the human world to the absolute decimation of the Soul Society.
This episode included scenes not found in the manga, such as Uryu Ishida discovering the truth about the Quincy's past in his father’s library, which helps explain his later motivations. 2. Part 2: "The Fundamental Virulence" (Episode 16 overall)
Kisuke Urahara sends "Hollowfied" pills to the Captains. Since Hollow power is "poison" to Quincies, it allows the Captains to forcibly take back their stolen Bankai.
Depending on which part you are watching, here is a detailed breakdown of the features and highlights from each Episode 3. 1. Part 1: "March of the Star Cross" (Episode 3 overall)