Marvel Television's Agents of SHIELD explored several storylines that would later be featured in the MCU over the course of its seven-season run. Initially developed to run adjacent to the MCU's theatrical releases, Marvel Television's Agents of SHIELD premiered in 2013 and explored the inner workings of the MCU's titular covert organization. Agents of SHIELD season 1 connected directly to MCU films including The Avengers, Thor: The Dark World, and Captain America: The Winter Soldier. However, from season 2 onwards, Agents of SHIELD's timeline became an entity in and of itself, exploring storylines completely separated from the MCU, some of which the larger franchise would adapt later on.
https://screenrant.com/agents-of-shield-marvel-storylines-before-mcu/