  The properties of the Lambda(1405) resonance are key ingredients for
determining the antikaon-nucleon interaction in strangeness nuclear physics,
and the novel internal structure of the Lambda(1405) is of great interest in
hadron physics, as a prototype case of a baryon that does not fit into the
simple three-quark picture. We show that a quantitative description of the
antikaon-nucleon interaction with the Lambda(1405) is achieved in the framework
of chiral SU(3) dynamics, with the help of recent experimental progress.
Further constraints on the Kbar N subthreshold interaction are provided by
analyzing pi Sigma spectra in various processes, such as the K-d -> pi Sigma n
reaction and the Lambda_c -> pi pi Sigma decay. The structure of the
Lambda(1405) is found to be dominated by an antikaon-nucleon molecular
configuration, based on its wavefunction derived from a realistic Kbar N
potential and the compositeness criteria from a model-independent weak-binding
relation.
