Sit-in started back in the 1960s during the civil rights movement as a peaceful way to protest something. Instead of violence they would sit in a spot until they were physically take away. Some of there more famous sit-in were the Greensboro sit-in and the reach sit-in by leaders of the NAACP
The Greensboro sit-in:
This sit-in was located in Greensboro, North Carolina. This was one of the most famous sit-ins during the civil rights movement, even though it's not talked about a lot. The four men that went by David Richmond, Franklin McCain, Ezell Blair and Josef McNeil were the ones who started protesting. The reason this started was because server would only server whites they refused to serve blacks so they sat there until they got what the wanted. This sit-in was successful and Woolworth department store chain removed it policy on racial segregation in the south.
NAACP sit-in:
Just recently on January 3, 2017 there was a sit in at the attorney generals office in New York. Cornell William brooks the leader and other high ranked member of the NAACP went to Jeff Sessions office and were protest agin him getting into office, because of his racist background. This situation hasn't been resolved yet.