Tensegrity can be considered as an innovative structural concept. Its development was initially largely linked with artistic activities. Following parallel design processes, most notably for the early stages, Art and Structural Engineering end up in an Art of Structural Engineering in case of Tensegrity systems. For them the coupling between Forms and Forces is very tight, and some examples testify this relation that can be studied within the framework of the theory of the systems, by advancing the notion of relational structure. The time of realizations is arrived, three of them are displayed: sculptures by Kenneth Snelson, double layer tensegrity grids ("Tensarch" project) and foldable footbridges.