A number of problems related to understanding diffuse interstellar clouds are the focus of this contribution. Observations are discussed relating to the high velocity clouds, to the morphology of diffuse interstellar clouds and to the time variability of features in the diffuse clouds. Abundances and ionization issues are dealt with as needed. In some of these areas, progress may be substantial over the next few years, through observation and modeling, but in others, it may be that a new generation of space satellites will be required to make substantial progress.