  Recently, the compositeness, defined as the norm of a two-body wave function
for bound and resonance states, has been investigated to discuss the internal
structure of hadrons in terms of hadronic molecular components. From the
studies of the compositeness, it has been clarified that the two-body wave
function of a bound state can be extracted from the residue of the scattering
amplitude at the bound state pole. Of special interest is that the two-body
wave function from the scattering amplitude is automatically normalized. In
particular, while the compositeness is unity for energy-independent
interactions, it deviates from unity for energy-dependent interactions, which
can be interpreted as a missing-channel contribution. In this manuscript, we
show the formulation of the two-body wave function from the scattering
amplitude, evaluate the compositeness for several dynamically generated
resonances such as $f_{0} (980)$, $\Lambda (1405)$, and $\Xi (1690)$, and
investigate their internal structure in terms of the hadronic molecular
components.
