Concentrated colloidal suspensions are a well-tested model system which has a
glass transition. Colloids are suspensions of small solid particles in a
liquid, and exhibit glassy behavior when the particle concentration is high;
the particles are roughly analogous to individual molecules in a traditional
glass. Because the particle size can be large (100 nm - 1000 nm), these samples
can be studied with a variety of optical techniques including microscopy and
dynamic light scattering. Here we review the phenomena associated with the
colloidal glass transition, and in particular discuss observations of spatial
and temporally heterogeneous dynamics within colloidal samples near the glass
transition. Although this Chapter focuses primarily on results from
hard-sphere-like colloidal particles, we also discuss other colloidal systems
with attractive or soft repulsive interactions.Comment: Chapter of "Dynamical heterogeneities in glasses, colloids, and
granular media", Eds.: L. Berthier, G. Biroli, J-P Bouchaud, L. Cipelletti
and W. van Saarloos (Oxford University Press, to appear), more info at
http://w3.lcvn.univ-montp2.fr/~lucacip/DH_book.ht