I will introduce the TRAPPIST-1 system, which is comprised of
seven transiting, Earth-sized planets orbiting a very small
star, about a tenth the size of our Sun in mass and radius.
This system may yield the best chance of studying the atmospheric
compositions of temperate, Earth-sized planets with the James
Webb Space Telescope, and has become a focal point for the
exoplanet and planetary science communities. I will report on
ongoing efforts by an international team to measure the masses,
radii, densities, and orbits of the planets in this system with
the Kepler and Spitzer Space Telescopes (RIP), HST, and ground-based
telescopes.

I will describe the transit-timing technique, and the dynamical basis
for measuring the planets' masses and orbital parameters. The
planets' compositions can be ascertained from dynamical modeling,
and I will give an update on these efforts, and the implications for
their compositions, for planet formation, and place this system in
the context of measurements of other exoplanets' properties. I will
conclude by discussing future prospects for the study of this system
and for finding others like it.