  We discuss various models of ion transport through cell membrane channels.
Recent experimental data shows that sizes of ion channels are compared to those
of ions and that only few ions may be simultaneously in any single channel.
Theoretical description of ion transport in such channels should therefore take
into account interactions between ions and between ions and channel proteins.
This is not satisfied by macroscopic continuum models based on
Poisson-Nernst-Planck equations. More realistic descriptions of ion transport
are offered by microscopic Brownian and molecular dynamics. One should also
take into account a dynamical character of the channel structure. This is not
yet addressed in the literature
