Towards the end of the 20th century, biology seems to have replaced physics as the leading scientific discipline. At the beginning 21st century, the potential impact of biology on the fate of mankind has placed this discipline in the limelight of public interest as well. It is therefore important that biologists leave the ivory tower of their laboratories and explain to the public what they do, how they do it, and what they want to achieve. In the first part of this volume six leading biologists present their views on the principles nature uses to generate complex organisms such as man, and on strategies such complex organisms use to protect their integrity in a hostile environment. The scientific process is revealed as an intellectual endeavor aimed at goals that enrich our culture rather than threaten it. The chapters are lectures read at a symposium on the occasion of the 40th anniversary of the Max-Planck-Institute of Immunobiology (Freiburg, Germany). Aimed at a general audience without being trivial