The preponderance of binary systems in all known stellar populations makes them exciting dynamical agents for research on topics as varied as
star formation, star-cluster dynamics and the interiors of young and old stars. Today we know that the Galactic-field binary population is
probably a dynamically evolved version of the Taurus-Auriga pre-main sequence population, and that the initial distributions of binary-star
orbital elements are probably universal. Furthermore, N-body calculations tentatively suggest that OB stars form in energetic binaries near
cluster cores, and that binaries with 'forbidden' orbital elements that are produced in stellar encounters, may turn out to be very useful windows
into stellar interiors, potentially allowing tests of pre-main sequence evolution theory as well as of models of main-sequence stars.