Abstract: The invention relates to a device for localizing tracking bodies (10), comprising at least one tracking body which is placed inside a physiological structure, and a means which is situated outside of the structure and which consists of sensor clusters (20) in a sensor cluster arrangement (55) as well as a method for localizing and influencing the tracking body. The tracking body is provided in the form of a body which is characterized by a finite remanent magnetization with a variable magnetic dipole moment and an anisotropic magnetic dipole field resulting therefrom. The sensor clusters (20) are provided in the form of a plurality of gradiometer sensors (30) with a specific measuring geometry. Optionally, physical/chemical properties and/or a trajectory of the tracking body may be altered in a specific manner by an externally acting magnetic field (H) and/or physiological processes in the environment of the at least one tracking body.