As we mark Martin Luther King Jr's birthday, Martha Teichner talks with some of those who were engaged from the very beginning of the civil rights movement: Arthenia Joyner, who was a Black high school student who took part in a sit-in at a Whites-only lunch counter in Tampa, Fla.; Jawana Jackson, who as a child participated with her mother in the Selma-to-Montgomery march in the wake of "Bloody Sunday"; and attorney Fred Gray, who won four civil rights cases before the Supreme Court by the age of 35.