Targeted drug delivery to tumors remains a challenging area in drug delivery research. While significant progress has been made in controlled drug delivery technologies, achieving effective targeted delivery to solid tumors is still a major challenge. The clinical impact of targeted drug delivery lies in its ability to specifically target a drug or drug carrier to minimize systemic toxic effects. However, many challenges remain in identifying successful targeted drug delivery strategies, including understanding the transport of drug or drug carrier to the target site after intravenous administration and the body's response to drug delivery systems. The concept of "passive targeting" is based on drug accumulation in areas around tumors with leaky vasculature, known as the enhanced permeation and retention (EPR) effect. However, most nanoparticles accumulate in other organs, such as the liver, spleen, and lungs, indicating that passive targeting is not selective. "Active targeting" refers to specific interactions between drug/drug carrier and target cells, usually through ligand-receptor interactions. However, the presence of a tumor-targeting ligand does not always result in increased accumulation of nanoparticles in tumors, suggesting that active targeting does not automatically translate into effective delivery to the entire tumor. Nanoparticle properties, such as size, shape, and surface characteristics, significantly influence their biodistribution and tumor targeting. PEGylation is used to extend the systemic circulation time of nanoparticles, which can enhance their accumulation in tumors. However, even with PEGylation, only a small fraction of nanoparticles reach the intended target site. Ligand-receptor interactions are essential for active targeting, but the expression of tumor-targeting receptors may not be homogeneous within a tumor or may change over time, making it difficult to achieve effective targeting. The concept of "magic bullet" in drug delivery refers to a system that delivers the majority of a drug payload to the intended target without significant effects on non-target tissues. However, current technologies have not yet achieved this goal. The reality of tumor targeting is complex, involving factors such as tumor heterogeneity, the dynamic nature of cancer cells, and the challenges of achieving effective drug delivery to solid tumors. Despite these challenges, nanoparticle-based drug delivery systems represent an exciting and promising advance in the treatment of cancer and other diseases. However, further research is needed to develop truly targeted drug delivery systems that can effectively deliver drugs to specific sites in the body.Targeted drug delivery to tumors remains a challenging area in drug delivery research. While significant progress has been made in controlled drug delivery technologies, achieving effective targeted delivery to solid tumors is still a major challenge. The clinical impact of targeted drug delivery lies in its ability to specifically target a drug or drug carrier to minimize systemic toxic effects. However, many challenges remain in identifying successful targeted drug delivery strategies, including understanding the transport of drug or drug carrier to the target site after intravenous administration and the body's response to drug delivery systems. The concept of "passive targeting" is based on drug accumulation in areas around tumors with leaky vasculature, known as the enhanced permeation and retention (EPR) effect. However, most nanoparticles accumulate in other organs, such as the liver, spleen, and lungs, indicating that passive targeting is not selective. "Active targeting" refers to specific interactions between drug/drug carrier and target cells, usually through ligand-receptor interactions. However, the presence of a tumor-targeting ligand does not always result in increased accumulation of nanoparticles in tumors, suggesting that active targeting does not automatically translate into effective delivery to the entire tumor. Nanoparticle properties, such as size, shape, and surface characteristics, significantly influence their biodistribution and tumor targeting. PEGylation is used to extend the systemic circulation time of nanoparticles, which can enhance their accumulation in tumors. However, even with PEGylation, only a small fraction of nanoparticles reach the intended target site. Ligand-receptor interactions are essential for active targeting, but the expression of tumor-targeting receptors may not be homogeneous within a tumor or may change over time, making it difficult to achieve effective targeting. The concept of "magic bullet" in drug delivery refers to a system that delivers the majority of a drug payload to the intended target without significant effects on non-target tissues. However, current technologies have not yet achieved this goal. The reality of tumor targeting is complex, involving factors such as tumor heterogeneity, the dynamic nature of cancer cells, and the challenges of achieving effective drug delivery to solid tumors. Despite these challenges, nanoparticle-based drug delivery systems represent an exciting and promising advance in the treatment of cancer and other diseases. However, further research is needed to develop truly targeted drug delivery systems that can effectively deliver drugs to specific sites in the body.