This chapter describes chromatin dynamics using stochastic modeling and polymer physics. It summarizes briefly modeling and analysis approaches that goes beyond classical Brownian motion and reviews how the cell imposes biological constraints on molecular motion. The chapter shows how single-particle trajectory data can be used to recover the chromatin organization and the ensemble of interactions it experiences. Trajectories of an individual particle inside a fluid, on the chromatin or a membrane, are usually described and analyzed in the physical literature using the Smoluchowski’s limit of the Langevin equation. To extract biophysical parameters from Single-Particle Trajectory of a chromatin locus, a physical model for the locus motion is needed. The dynamics of the locus reflects the local chromatin organization and the ensemble of interactions it experiences. The relation between chromatin structure/organization can be described using the dynamics of a tagged monomer when the chromatin is described as a static fractal globule.