 The cluster ion spectrometry, CIS, experiment on the four cluster spacecraft measures the full three-dimensional ion distribution of major magnetospheric ions from thermal energies to about 40 keV slash E using two different instruments, a composition and distribution function analyzer, CIS-1 slash codiff, and a hot ion analyzer, CIS-2 slash HA. The CIS instruments were commissioned from early September 2000 to mid-January 2001, and the operation phase began on February 1, 2001. First results of the CIS instruments show high-level performances and capabilities in various magnetospheric and solar wind magnetosphere interaction measurements, including central plasma sheet, magnetopause crossings, magnetosheath, solar wind, CUSP, and auroral regions observations at radial distances of 4 to 6 Earth radii. These results open a new area in magnetospheric and solar wind magnetosphere interaction physics with multi-spacecraft measurements using identical instruments. This article was authored by H. Reem, C. O. Eston, J. M. Boscade, and others. We are article.tv, links in the description below.