A collection of state-of-the-art reviews of diverse topics covering almost all the major areas of modern quantum chemistry. The current focus in the discipline of chemistry - synthesis, structure, reactivity and dynamics - is mainly on control. A variety of essential computational tools at the disposal of chemists have emerged from recent studies in quantum chemistry. The acceptance and application of these tools in the interfacial disciplines of the life and physical sciences continue to grow. The new era of modern quantum chemistry throws up promising potentialities for further research. This work is a joint endeavour, in which renowned scientists from leading universities and research laboratories spanning 22 countries present 59 in-depth reviews. Along with a personal introduction written by Professor Walter Kohn, Nobel laureate (Chemistry, 1998), the articles celebrate the scientific contributions of Professor Robert G. Parr on the occasion of his 80th birthday. The contributors include W. Kohn, M. Levy, R. Pariser, B.R. Judd, E. Lo, B.N. Plakhutin, A. Savin, P. Politzer, P. Lane, J.S. Murray, A.J. Thakkar, S.R. Gadre, R.F. Nalewajski, K. Jug, M. Randic, G. Del Re, U. Kaldor, E. Eliav, A. Landau, M. Ehara, M. Ishida, K. Toyota, H. Nakatsuji, G. Maroulis, A.M. Mebel, S. Mahapatra, and many others.