N. Echols,
R. W. Grosse-Kunstleve,
P. V. Afonine,
G. Bunkóczi,
V. B. Chen,
J. J. Headd,
A. J. McCoy,
N. W. Moriarty,
R. J. Read,
D. C. Richardson,
J. S. Richardson,
T. C. Terwilliger and
P. D. Adams The foundations and current features of a widely used graphical user interface for macromolecular crystallography are described.