This text is the proceedings volume of a NATO Advanced Research Workshop, held in Eliat, Israel, April 5th-8th, 2000. It brings together interdisciplinary contributions ranging from applied mathematics, theoretical physics, quantum chemistry and molecular biology, all addressing different facets of the problem to connect the many scales of the computer simulation of many systems of interest in chemistry - polymetric materials, biological molecules, clusters, surface and interface structure. Emphasis is placed on the multigrid technique and its applications, ranging from electronic structure...