Localization studies often involve tracking the distribution of nanoparticles within biological systems over time. Common methods include: 1. Radioactive Labeling: Uses radioactive isotopes to track nanoparticles in vivo. 2. Magnetic Resonance Imaging (MRI): Employs magnetic nanoparticles to visualize their biodistribution. 3. Computed Tomography (CT): Uses X-ray imaging to detect nanoparticles labeled with contrast agents. 4. Bioluminescence Imaging: Involves nanoparticles that emit light upon interaction with specific biological molecules.