Understanding of mechanisms of action of biological molecules is the base that enables planned intervention into biological systems with foreseeable effects. The obtained knowledge can be used for the well being of humanity and life on Earth and last but not least the developed of new products such as drugs may stimulate economic growth and contribute to sustainable development. Structural studies combined with others methods of biochemistry, molecular biology, cell biology and physiology enable studies of molecular mechanisms, their specificity and physiological role. Our main achievements are determination of the crystal structure of the p41 fragment and cathepsin L (Gunčar et al.., 1999) and the crystal structure of cathepsin C (Turk et al., 2001). The first structure revealed the mechanism by which the the p41 fragment can recognize various human cathepsins and suggested and suggested further development of plat inhibitors for potential use in agriculture. The crystal structure of cathepsin C explained the mechanism by which cathepsin C can selectively activate trypsin like serine proteases involved in response of immune and inflammatory defense systems. Understanding of proteolytic process under investigation is besides the scientific point of view relevant also for pharmaceutical industry. The outstanding level of research was indicated by invited lectures at scientific drug research meetings (for instance "From genes to drugs via crystallography", Erice, Italy, Maj 2002; "Biochemical Aspects of Health and Disease." Biochemical Society Meeting, UK. December, 2002.), the invitations for publishing the review articles (for instance (D. Turk in G. Gunčar: Lysosomal cysteine proteases: promising drug targets, Biol. Cryst., 2003). The achievements of the group have been noticed by the scientific community as indicated by the citations of the group leader, who is with over 2200 citations (almost all citations are from the period of the last 10 years) among the most cited Slovenians authors. The organization of international school for macromolecular crystallography with one of the pioneers of macromolecular crystallography L.N. Johnson in Erice, Italy 2000 is by itself an acknowledgment of the international excellency of the research program Structural biology.