  Mira variables share essential characteristics: High visual amplitude,
periods of hundreds of days, red colors (spectral types M, S, and C), and the
presence of emission lines at some phases. They are fundamental mode pulsators,
with progenitor masses ranging from >1 to several solar masses. In this review,
we summarize what is known from modeling and observational studies, including
recent measurements from optical and IR interferometry, and studies involving
large samples of stars particularly in the Magellanic Clouds. While we have a
good idea of how these stars fit into the big picture of stellar evolution,
many important details remain to be settled by a combination of more ambitious
models and new observational techniques. Carrying on observations of bright
Mira variables will be essential for interpreting observations of large numbers
of fainter sources as well as for assessing the completeness and accuracy of
the models.
