My aim is to examine Aristotle's hylomorphism as a model for scientific explanation of living beings. I argue that the issue of matter-form relation should be connected with the opposition between the necessity of material and efficient causes and the teleology of forms. Form (as "telos") is a principle able to organize the appropriate conjunction of material and efficient causes. Formal and final causes are not a trick for filling the "gap in causation", nor are they bare heuristic tools for inquiring into the "true" causes. The primacy of formal and final causes guarantees an appropriate account of material and efficient causes inasmuch as form and "telos" are responsible for bending and organizing the original dispositions of the material elements.