Traditionally, morphology is seen merely as an auxiliary subdiscipline of biology and other fields. Allegedly, it does not provide explanations for phenomena but merely describes forms as a preliminary step in their analysis. Here, the view is defended that forms, and hence morphology, can also take over an important explanatory function and even, ultimately, constitute the explanatory level fundamental to biology as a distinct science. According to this thesis, the form of organisms and their parts provide the only specifically biological causal factors. Nothing but the form, the specific spatial arrangement of matter, determines the peculiarity of organisms’ ways of being. Therefore, biological explanation must start from specific structures. These structures provide the respective boundary conditions for harnessing the general laws of nature, thus determining their trajectory. Ultimately, then, forms play the most fundamental explanatory role in biology.