ACA currently has about 2,200 members from countries spanning the globe.  Scientists in every stage of their careers benefit from this diverse scientific community.  Members are free to join one or several of ACA's 12 Scientific Interest Groups (SIGs).  Each SIG provides focus on a specialty area and have a direct impact upon the program at the annual meetings.  They offer members opportunities for networking within their field while expanding their skills and expertise outside their field.  There are no additional fees to join a SIG.  SIGs include: Biological Macromolecules, Fiber Diffraction, General Interest, Materials Science, Neutron Scattering, Powder Diffraction, Service Crystallography, Small Angle Scattering, Small Molecules, Synchrotron Radiation and Young Scientists.