During development, dynamic cell behaviours are carefully orchestrated to ensure that morphogenesis is completed within the correct developmental time frame, but how is this achieved? Erina Kuranaga and colleagues (p. 1493) have been examining genital morphogenesis in Drosophila and report that apoptosis controls the speed of looping morphogenesis in the fly's male terminalia. The terminalia is an asymmetric looping organ in which the internal genitalia (spermiduct) loops around the hindgut. During maturation of the internal genitalia, the male terminalia rotates 360° clockwise. Previous work has shown that the adult male terminalia is incorrectly orientated in mutants for apoptotic signalling. Now, using time-lapse imaging, the researchers show that, in normal flies, genitalia rotation accelerates as development proceeds but that this acceleration is impaired when the activity of apoptotic signalling components is reduced. The researchers propose that apoptosis drives the movement of cell sheets during the morphogenesis of male terminalia, thereby ensuring that morphogenesis is completed within a limited developmental time frame.