In this talk, I will talk about the tagged particle in the symmetric simple exclusion process (SSEP) in an extreme density regime, where the initial distribution is the Bernoulli product measure with a density either vanishing or converging to one. I will explain the limits of the tagged particle under a proper space-time scaling in different scenarios, which are either Fractional Brownian motion, Brownian motion or Brownian motion with Brownian barriers. Based on an on-going project with Tertuliano Franco and Patrícia Gonçalves.