The sol-gel transition (also known as gelation) is simply a change from a liquid state to a gel state. In the liquid state, components dispersed in the liquid are relatively free to move about. In the gel state, these subunits bond together to form a network extending throughout the whole substance (see figure 1). The network gives the material an elasticity: a solid-like property [1, p. 95].
The composition of the subunits and the bonds between them strongly affect the properties of the gel [1, p. 95].
You can witness the sol-gel transition by curing epoxy , making a dessert with gelatin [ 2 ], or making jam with pectin [ 3 ]. The authors of Phase Behavior and Rheology of Attractive Rod-like Particles observe a sol-gel transition in a colloidal dispersion of rod-shaped particles.
 R. Jones, "Soft Condensed Matter," Oxford University Press Inc., New York (2002).
 B. Cole, "Gelatin," http://www.gelatin.co.za/gltn1.html, (accessed Nov. 4, 2009).
 S. Bowling, "On the Jelling of Jelly," Alaska Science Forum, http://www.gi.alaska.edu/ScienceForum/ASF8/887.html, (Aug. 20, 1988).