Division Machinery Tagged: An international consortium of labs has been testing the feasibility of large-scale screening for insights into the function of mammalian proteins by expressing a tagged version of proteins from bacterial artificial chromosomes harbored in mammalian cells. Depending on the tag used, Hutchins et al. (p. 593 , published online 1 April) were able to monitor localization of tagged proteins by microscopy or to isolate interacting proteins and subsequently identify the binding partners by mass spectrometry. Applying the technology to proteins implicated in control of cell division revealed about 100 protein machines required for mitosis.