I'll introduce a particular class of fundamental string configurations in the form of closed loops stabilized by their internal dynamics. Then, I'll describe their classical treatment and embedding in models of string cosmology, present their quantum version in flat space and the semiclassical limit that provides the microscopic description of certain type of black rings. I'll show the parametric matching between the degeneracy of microstates and the entropy of the supergravity solution and conclude by commenting on the progress towards a similar construction on an AdS background.