Size enlargement by agglomeration, the technical application of a natural phenomenon, includes the uncontrolled, unwanted, and desired adhesion of solid particles. Latest since the fundamental publications of RUMPF in 1958, it has been recognized as one of the unit operations of mechanical process technology. in spite of its long history and the meanwhile wide distribution of applications, a systematic approach to the development of new processes is not normally used. Although a large interdisciplinary pool of knowledge exists, processes for new applications are almost exclusively based on empirical similarity. Methods for the systematic development of new technologies for the size enlargement by agglomeration and the selection of peripheral systems are discussed. Special considerations related to desired, unwanted or uncontrolled agglomeration in particle engineering are also mentioned.