The chapter explores the evolving landscape of in vivo infiltrationIn vivo infiltration techniques for the targeted deliveryTargeted delivery of nanoparticlesNanoparticles (NPs) in biomedical applicationsBiomedical applications. With the growing interest in nanotechnologyNanotechnology, the capability to accurately target and deliver therapeutic agents to specific tissuesTissue or cellsCell has become a focal point of research. This chapter delves into the various methods of infiltrating nanoparticlesNanoparticles (NPs) into biological systems, emphasizing their mechanisms, efficiency, and challenges. Techniques such as intravascularIntravascular nanoparticle delivery, intratumoral, and transdermalTransdermal nanoparticle delivery delivery are examined, with a focus on how they are tailored to improve the absorption and effectiveness of nanoparticlesNanoparticles (NPs) in therapy. Furthermore, the chapter highlights the role of advanced imaging and monitoring toolsNanoparticle monitoring tools in optimizing these techniques, ensuring accurate tracking and controlled releaseControlled release of nanoparticlesNanoparticles (NPs) in vivo. Case studies and recent advancements are presented to illustrate the practical applications of these methods for addressing diseases like cancer, cardiovascularCardiovascular disorder treatment disorders, and neurologicalNeurological disease therapy conditions. The chapter concludes by addressing the future directions and potential obstacles in the field, including the need for improved biocompatibilityBiocompatibility, minimization of off-target effectsOff-target effects, and overcoming physiological barriersPhysiological barriers. Through a comprehensive overview of current infiltration strategies, this chapter seeks to offer a fundamental understanding for researchers and practitioners aiming to fully leverage the potential of nanoparticlesNanoparticles (NPs) in clinicalNanoparticles in clinical trials applications.