We summarize and extend evidence that the deconfinement phase transition in Yang-Mills theories can be viewed as change of effective non-perturbative degrees of freedom and of symmetries of their interactions. In short, the strings in four dimensions (4d) at temperatures below the critical temperature Tc are replaced by particles, or field theories in 3d at T>Tc. The picture emerges within various approaches based, in particular, on dual models, lattice data and field theoretic models. We concentrate mostly on the lattice data, or on the language of quantum geometry.