|The application of quantum theory to cosmology has defined the research of Alexander Vilenkin for more than twenty years. His pursuit of questions about the origin and the destiny of the universe became possible, however, only after he left his native Russia. A Jew, born in the Ukraine, he was graduated from Kharkov State University with a degree in physics, but could neither gain admission to a doctoral program nor find work in his field. Emigrating in 1976, he was temporarily resident in Italy when he applied and was accepted at the State University of New York in Buffalo. Awarded a Ph.D. in physics the next year, he accepted a post-doctoral position at Case Western Reserve University in the physics of metals even as he conducted research in an area he found far more intriguingblack holes. In 1978, Dr. Vilenkin joined the faculty of Tufts University where he was named a professor of physics in 1987 and appointed director of the Tufts Institute of Cosmology two years later. His first major paper on inflation and quantum cosmology, published in 1982, explained how the universe could have been created ex nihilo through quantum energy spacetime fluctuations. In another paper, the following year, he made the then astonishing suggestion that almost all inflationary models are eternal once the process starts it continues without end like a chain reaction, stopping in one region of space only to start in another, ultimately spawning an infinite number of pocket universes. His variant account for the universes birth by quantum tunneling from nothing, involved a leap from no size at allzero radiusto a radius large enough for inflation to take over. Continuing to explore the implications of this idea, he and Arvinde Borde showed mathematically that a universe eternally inflating toward the future cannot be geodesically complete in the past, so that there must have existed in the indefinite past an initial singularity, an ultimate boundary, or beginning. Dr. Vilenkin is also a leading developer of the concept of cosmic stringsdense, linear defects in the fabric of space formed in the hot early universe, which he once thought might have a role in transforming matter and energy into galaxies. With Jaume Garriga, he has recently argued that there are an infinite number of regions of space the same size as our observable universe, but that their historiesor things that could possibly happen within these realms, including the evolution of intelligent lifeare finite, so that every possible version of history will have occurred elsewhere. They call their work a metaphysical exercise and name their concept many worlds in one. A fellow of the American Physical Society, Dr. Vilenkin has been the recipient of a National Science Foundation Presidential Young Investigator Award and a research grant from the John Templeton Foundation. He is the author of more than 160 scientific papers and (with E. Paul Shellard) the book, Cosmic Strings and Other Topological Defects (Cambridge University Press, 1994 and 2000).