Form, force and flamboyance

The diagram of forces mentioned in the well-known quote from D’Arcy Thompson’s biblical book can be recognised in various guises throughout the reviews in this special issue of Current Biology on cell form and physics. The force diagram is perhaps most strikingly apparent in a structure that has not terribly much to do with cell shape per se — the mitotic spindle, discussed by Sophie Dumont and Tim Mitchison. This complex apparatus, the prime task of which is the segregation of chromosomes, is determined in its form and function by the forces generated by its molecular machines. It is perhaps a curious twist of history that only now — after decades of deciphering its molecular make-up — we are beginning to understand the spindle as a purely physical, mechanical object, while D’Arcy Thompson could formulate a great deal of his physical principles in blissful ignorance of the underlying biological machinery. And with the current renaissance (or naissance) of physical thought in cell biology, Thompson’s book might be moving along from the apocryphal towards the canonical. In the case of cell form, the force diagram is essentially a balance between ‘intrinsic’ and ‘extrinsic’ forces. Depending on the cell being studied, the forces can be carried by different cellular structures; intrinsic forces may, for instance, be generated by the cytoskeleton, while extrinsic forces are particularly relevant in multicellular organisms Editorial