Between 1900 and 1930 colloid chemistry, a branch of physical chemistry, gained crucial importance for the understanding of vital phenomena. To many it seemed that the properties of colloids would differ from those of ordinary matter, paralleling the specific properties of protoplasm, the living substance . The application of theoretical concepts and experimental models of colloid chemistry to biological problems shaped Biocolloidology as a new research program, which appeared promising for the exploration of organic processes such as mitotic cell division, (...) growth, muscle contraction and movement. Biocolloidology could simultaneously absorb the quest for a physical-chemical explanation of life and the (post)-romantic notion of organic nature as a container of creative and vital forces that was central to life-philosophy. At least until the late 1920s, it is argued, the merging of different scientific and philosophical metaphors made Biocolloidology and the concept of protoplasm highly appealing in a broad cultural context. (shrink)