 The cluster mission was launched in 2000 as ESA's first cornerstone project, along with SOHO. Two Russian Soyuz rockets were used to deliver two cluster spacecraft into their proper orbits by July and August of that year. The four satellites reached their final tetrahedral constellation by the end of August. The commissioning of 44 instruments was completed five months later, ensuring optimal use of their observational potential. The mission was declared operational on February 1, 2001. The main goal of the cluster mission is to study small-scale plasma structures in key plasma regions such as the solar wind, bow shock, magnetopause, polar cusps, magnetotail, and auroral zones. With its unique capabilities of three-dimensional spatial resolution, cluster plays a major role in the International Solar Terrestrial Program, ISTP. The payload consists of state-of-the-art plasma instrumentation to measure electric and magnetic fields from quasi-static, up to high frequencies, and electron and ion distribution functions from energies nearly 0EV to a few MEV. Science operations are coordinated by the Joint Science Operations Center, JSOC, at Rutherford Appleton Laboratory in the UK and implemented by the European Space Operations Center, ESOC, in Darmstadt, Germany. A network of eight national data centers has been set up for raw data processing, physical parameter production, and distribution to end-users worldwide. This article was authored by C. P. Escubette, M. Ferringer, and M. Goldstein. We are article.tv, links in the description below.