Eric G. Adelberger
 Department of Physics
 University of Washington

It is remarkable that questions about gravitation, the oldest known
interaction in physics, are again at the center of physics and that
small-scale experiments can address important open issues.
Modern theoretical ideas (new stringy particles and extra dimensions)
hint that both Einstein's Equivalence  Principle and Newton's
Inverse-Square Law may not be exact. I will discuss motivations,
techniques, and results of  the Eot-Wash group's recent and ongoing
tests of both of these long-accepted principles:  verification of the
Strong Equivalence Principle at differential acceleration precisions
better than 3 times 10^-13 cm/s^2 and tests of the Inverse-Square
Law for length scales down to 100 micrometers.