  Two-pole structures refer to the fact that two dynamically generated states
are located close to each other between two coupled channels and have a mass
difference smaller than the sum of their widths. Thus, the two poles overlap in
the invariant mass distribution of their decay products, creating the
impression that only one state exists. This phenomenon was first noticed for
the $\Lambda(1405)$ and the $K_1(1270)$, and then for several other states.
This report explicitly shows how the two-pole structures emerge from the
underlying universal chiral dynamics describing the coupled-channel
interactions between a heavy matter particle and a pseudo-Nambu-Goldstone
boson. Furthermore, we predict similar two-pole structures in other systems
dictated by chiral symmetry, such as the isospin $1/2$
$\bar{K}\Sigma_c-\pi\Xi'_c$ coupled channel, awaiting experimental discoveries.
