Plant adaptation is a fundamental process in plant breeding. It was the first criterion in the initial domestication of plants thousands of years ago. Adaptedness is generally a quantitative complex feature of the plant, involving many traits, many of which are quantitative. Adaptation to stresses like cold, drought or diseases are among the most central problems in a world grappling with global food security. Modern plant breeding, based on mendelian genetics, has made plant improvement more effective and more precise and selective. Molecular genetics and genetic engineering has considerably increased this selectivity down to single genes affecting single traits. The time has come when plant breeding efficiency may cause loss of genetic resources and adaptation. In these proceedings an effort is made to merge modern plant breeding efficiency with ecological aspects of plant breeding, reflected in adaptation. It is hoped that this merger results in more sustainable use ofgenetic resources and physical environments. The book is based on 10 keynotes addressing a wide spectrum of themes related to adaptation. In addition each subject is further elaborated in up to three case studies on particular plant species or groups of plants. The keynotes do in fact overlap to some degree and there are articles in this volume that seemingly contradict each other, a common aspect in advanced fields of research. The keen reader may conclude that, in a world where climates and environments are under continuous change and where human society is more and more polarized into a developed and a developing part, adaptation of our cultivated plants has different constraints on yields depending on ecology, and indeed economy.