The CESNET e-infrastructure is a complex system of interconnected tools that provides a wide range of services necessary for transmission, storage and data processing. These include, for example, performance computing clusters with programs used in many areas, a large data repository used for data storage and sharing, multimedia communication tools making cooperation between distributed teams easier, and other services. These modern IT services are used for scientific and research work, and for problem solving focusing on a wide range of disciplines which are not confined to natural sciences, such as mathematics, physics, chemistry, biology and computer science, but also include, for example, humanitarian sciences and art. The extensive e-infrastructure is composed of four basic logically coherent components: