  A fresh approach to the data from experiments with hard sphere colloids
yields seminal insights into the glass transition. The precise determination of
the fraction of particles caged by their neighbours is unprecedented and
provides cornerstone of our study. We show that the so-called "dramatic
slowing" that accompanies super-packing is due to correlated cage fluctuations,
rather than caging per se. Their statistics establish that the amorphous
assemblies of caged particles are in states of self-organised criticality. The
implied connection between the onset of caging and the thermodynamic 1st order
freezing transition challenges the status quo, as does our contention that the
dynamically critical amorphous assemblies are precursory to that transition.
