The purpose of this chapter is to introduce the reader to the deep mixing method. In the deep mixing process, the ground is mixed in place while a binder is injected with the help of a mixing tool. After hardening, soil mix elements with improved mechanical and hydraulic characteristics are realized. This technology, originally developed in the 1960s for ground improvement works, has seen amazing growth in the past few decades. Today, the deep mixing method is used for a large scope of engineering projects, such as soil reinforcement, slope stabilization, support of embankment, and liquefaction mitigation. In addition, the soil mix elements are being increasingly used as structural elements, for the construction of earth-water retaining walls and cutoff walls, and even as an alternative to the classical foundation solution. Geo-environmental applications are also performed with the soil mixing remediation technology with the containment or the treatment of the contaminants directly into the ground.