The presence of microscopic particles, so-called non-metallic inclusions (NMI), cannot be entirely avoided during steelmaking. These NMIs usually negatively affect the mechanical properties of the final steel product or already cause problems during processing in the steel plant. Tracing techniques are applied to track the particle evolution to improve the detailed understanding of inclusion behavior over different process steps. One approach is to deliberately add rare earth elements (REE) to the melt and thus mark the inclusions. Another method determines and compares the natural REE fingerprint of inclusions and their potential sources. In the case of the REE pattern matches, the investigated auxiliary is supposed to contribute to the formation of the examined inclusion. Accurate analysis of the low REE concentrations by ICP-MS and LA-ICP-MS is essential for both concepts. The present study explains the principle and relevance of both approaches to meet the continuously increasing demands regarding steel quality.