  Lorentz and CPT invariance are among the symmetries that can be investigated
with ultrahigh precision in subatomic physics. Being spacetime symmetries,
Lorentz and CPT invariance can be violated by minuscule amounts in many
theoretical approaches to underlying physics that involve novel spacetime
concepts, such as quantized versions of gravity. Regardless of the underlying
mechanism, the low-energy effects of such violations are expected to be
governed by effective field theory. This talk provides a survey of this idea
and includes an overview of experimental efforts in the field.
