The Sassanid era refers to the period of the Sassanid Empire, which lasted from 224 to 651 CE. This empire was the last pre-Islamic Persian empire, known for its achievements in art, architecture, and culture. The Sassanids expanded their territory, reaching parts of the Middle East, Central Asia, and the Caucasus, and they were known for their conflicts with the Roman Empire. During the Sassanid era, Zoroastrianism became the state religion, influencing various aspects of life and governance. The empire is also recognized for its advancements in science, medicine, and philosophy, as well as its impressive architectural structures, such as the city of Ctesiphon.