This collection of essays by scientists from around the world honors Victor Frederick Weisskopf, one of the true luminaries of twentieth-century physics. Among the many breakthroughs his research has yielded have been the theory of the widths of energy levels of the electron, the "Clouded Crystal Ball" model of nuclear structure, and the "MIT Bag" model of hadronic matter. For his contributions to physics, Dr. Weisskopf has been awarded the Max Planck Medal, the J. Robert Oppenheimer Medal, and, most recently, the Karl Taylor Compton Award. In addition to being an accomplished researcher, Weisskopf is a passionate pianist, innovative administrator, inspired teacher, and tireless promoter of physics through his books, conference lectures, rewiev articles, and popular scientific writings. His deep interests in history, politics, and human affairs have made him an articulate advocate for the physics community worldwide. He has played a leading role in international collaborations in physics, most notably as Director General of CERN from 1961 to 1965. Weisskopf is an eloquent spokesman regarding the social and political responsibility of scientists. He may justly be called the senior statesman of science. The essays in this book are by some of the world's leading physicists, including seven Nobel Prize winners. The essays address topics ranging from Weisskopf's contributions to theoretical physics to more intimate views of his role as a teacher, friends, and humanist. For example, Hendrick B.G. Casimir writers on "Van der Waals Forces and Zeropoint Energy", Walter Thirring considers "Why is the Entropy of Black Holes so Big ?" , and Hans A. Bethe tells of "Life and Physics with Viki"? There are also contributions from Jerome I. Friedman, Henry W. Kendall, Lurray Gell-Mann, and a dozen others. For all his accomplishments, Victor Weisskopf remains a contemplative and unpretentious man. Throughout the world's scientific community he is known simply as Viki. The man and his work are revealed here by the collaborators, colleagues, and friends who know him best.