  The structures of the hyperon resonance $\Lambda (1405)$ and the scalar
mesons $\sigma$, $f_{0}(980)$, and $a_{0}(980)$ are investigated based on the
coupled-channels chiral dynamics with finite volume effect. The finite volume
effect is utilized to extract the coupling constant, compositeness, and mean
squared distance between two constituents of a Feshbach resonance state as well
as a stable bound state. In this framework, the real-valued size of the
resonance can be defined from the downward shift of the resonance pole
according to the decreasing finite box size $L$ on a given closed channel. As a
result, we observe that, when putting the $\bar{K}N$ and $K\bar{K}$ channels
into a finite box while other channels being unchanged, the poles of the higher
$\Lambda (1405)$ and $f_{0}(980)$ move to lower energies while other poles do
not show downward mass shift, which implies large $\bar{K}N$ and $K\bar{K}$
components inside higher $\Lambda (1405)$ and $f_{0}(980)$, respectively.
Extracting structures of $\Lambda (1405)$ and $f_{0}(980)$ in our method, we
find that the compositeness of $\bar{K}N$ ($K\bar{K}$) inside $\Lambda (1405)$
[$f_{0}(980)$] is 0.82-1.03 (0.73-0.97) and the mean distance between two
constituents is evaluated as 1.7-1.9 fm (2.6-3.0 fm).
