Ever increasing demand for more radiation resistant detectors from experiments such as those at the Large Hadron Collider has pushed the development of novel radiation resistant technologies. Recent developments in the laser processing of diamond have led to the construction of the first 3D diamond detectors: diamond detectors with graphitic electrodes embedded in the sensor material bulk rather than on the surface. This technology also presents interesting properties for the medical field, where 3D diamond detectors are also of interest. This thesis details some of the steps that were carried out between the fabrication of some of the first 3D diamond devices to the present day production and testing of the first 3D pixel devices and the first use of 3D diamond devices in Particle Physics experiments. This progress has in part been pushed by improvements in the laser processing techniques allowing the production of columns with lower resistances and more consistent properties. This thesis describes the fabrication of a number of these devices and details the experiments that these devices have undergone in a number of different conditions at the Diamond Light Source (Oxford), the Ruder Boskovic Institute (Zagreb), the Paul Scherrer Institute (Zurich), and the test beam facilities at CERN. This thesis also describes the simulations that were carried out to replicate the data obtained from some of the earlier devices, and hence understand how charge is collected in 3D diamond detectors and to explain some of the observed behavior of these devices.