The main task of architects is to design a building that provides safety, comfort, pleasure and an optimal living environment for its occupants. These demands should be met with the least possible amount of energy consumed, and should affect the environment as little as possible. This is why all of the building’s technological systems must be well controlled and synchronized. In contemporary buildings this rather complicated task can be fulfilled by using microelectronic-based building management systems. The purpose of this chapter is to introduce the fundamentals of microelectronic control systems, and to explain what building management systems are and how they operate. The chapter is divided into two parts. The first part deals with the basics of control systems; the possibilities, advantages and configurations of building management systems are presented in the second part.