We review a variety of measurements on model systems in the medium viscosity range which seem consistent with both thermodynamical (entropy vanishing) and dynamical (mode coupling) origins of glassy behavior and then examine behavior near and below Tgto seek relations between liquid fragility and the non‐exponential and non‐linear aspects of liquid relaxation processes. We include the model ionic system Ca(NO3)2–KNO3and analogs, van der Waals systems, and the covalently‐bonded system Ge‐As‐Se in which the relation of liquid properties to the vector percolation concepts of Phillips and Thorpe can be conveniently studied.With some basic phenomenology in the liquid state itself thereby established, we turn attention to longer length‐scale processes occurring in viscous liquid media. Among these will be the kinetics of nucleation of crystals, the freezing of microemulsion droplet sizes during continuous cooling of temperature sensitive microemulsions, and the freezing of chemical reactions during continuous cooling or continuous evaporation of solvent. The latter freezings can occur at temperatures which are far above the solvent glass transition temperature depending on solvent fragility, which may be a consideration in the strategies adopted by nature in preservation of plant and insect integrity in cold and arid climates.Finally we consider the slowing down which occurs in liquids with density maxima like water and SiO2which appear to have, as their low temperature metastable limits, spinodal instabilities (with associated divergences in physical properties) in place of the usual ideal glass transitions. So far little studied for lack of tractable slow systems, these offer a new and challenging arena for relaxation studies.