  The pole counting rule is a powerful and model-independent method to
distinguish a confining state from a hadronic molecule. It has been applied to
the explorations of $X(6900)$, $X_1(2900)$ as well as $Z_c(3900)$, $X(3872)$,
$X(4660)$, etc.. For $X(6900)$, both a confining state and a molecular state
are not excluded, because lacking of enough data. For $X_1(2900)$, the analysis
shows that it should be a $\bar{D}_1 K$ molecule, with $J^P=1^-$ and an
iso-singlet interpretation is much more favorable. Finally, it is noted that
almost all XYZ particles with exotic quantum numbers can be interpreted as
hadronic molecules. The $X(3872)$ is, however, more like a charmonium.
