  In the first one of these two lectures, I give an introductory review of
phase transitions in finite temperature field theories. I highlight the
differences between theories with global and local symmetries, and the
similarities between cosmological phase transitions and phase transitions in
superconductors. In the second one, I review the theory of defect formation in
finite temperature phase transitions, emphasising the differences between
systems with broken global and local symmetries. These same principles apply to
relativistic and condensed matter systems alike.
