This volume presents twelve important papers which have formed some the cornerstones of geometric analysis. Their subject matter ranges over the areas of conformal geometry, gauge theory, symplectic geometry, mean curvature, spectral theory, and general relativity. Among the authors and topics are: Morio Obata on the conjectures on conformal transformations of Riemannian manifolds; Richard Schoen on conformal deformation of a Riemannian metric to constant scalar curvature; Clifford Henry Taubes on the stable topology of self-dual moduli spaces; Karen Uhlenbeck on harmonic maps and classical solutions of the chiral model; Z. I. Szabó on the Lichnerowicz conjecture on harmonic manifolds (1990); and Ben Andrews and Haizhong Li on embedded constant mean curvature tori in the three-sphere. With a preface by Richard Schoen.