“…M-theory illustrates such configurations in elementary manner. M2-branes stretched between a pair of M5-branes or between M5-brane and M9-brane give rise to various strings, referred to as M-strings, first identified in [17] and further studied in [20,18,19,21], and E-strings, first identified in [22] and further studied in [23,24,25,26], which then combine with tensor multiplets to form non-Abelian multiplets. So far, except A-type theories, it has remained difficult to explicitly identify the underlying non-Abelian structure in terms of these building blocks.…”