This volume is a collection of the Nobel Lectures delivered by the prizewinners, together with their biographies and the presentation speeches at the award ceremonies in Stockholm for the period 2001 - 2005. Each Nobel Lecture is based on the work for which the laureate was awarded the prize. This volume of inspiring lectures by outstanding chemists and biochemists should be on the bookshelf of every keen student, teacher and professor of chemistry as well as of those in related fields. Below is a list of the prizewinners during the period 2001 - 2005 with a description of the works which won them their prizes.(2001) William S Knowles, Ryoji Noyori -- for their work on chirally catalyzed hydrogenation reactions & K Barry Sharpless -- for his work on chirally catalyzed oxidation reactions; (2002) John B Fenn, Koichi Tanaka -- for their development of soft desorption ionization methods for mass spectrometric analyses of biological macromolecules & Kurt Wüthrich -- for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution; (2003) Peter Agre -- for the discovery of water channels & Roderick MacKinnon -- for structural and mechanistic studies of ion channels; (2004) Aaron Ciechanover, Avram Hershko & Irwin Rose -- for the discovery of ubiquitin-mediated protein degradation; (2005) Yves Chauvin, Robert H Grubbs & Richard R Schrock -- for the development of the metathesis method in organic synthesis.