The existence of nuclear states of $\overline{K}$ mesons and $\eta$ mesons has been expected for about thirty years. The physical interest of this field is related to a new mechanism of nuclear binding generated by excitations of the internal nucleon structure. Despite being short lived such states might offer a new and interesting nuclear spectroscopy.
Despite long and extensive experimental search, the existence and properties of such states are still elusive.
Some similarities and related questions of the $\eta$ and $\overline{K}$ cases will be shown. Possible origin of the experimental difficulties related to weak production rate and large widths of such states will be discussed. I will try to indicate usefulness of the recent AMADEUS/KLOE measurements.