AR and breast cancer: However, these molecules primarily interact with certain types of proteins that are overexpressed or explicitly expressed at the tumor sites, neglecting patient‐specific tumor differences for the same type of cancer.[24] To overcome this challenge, we utilized in vivo phage display to identify a tumor‐targeting peptide, AREYGTRFSLIGGYR (termed as AR), which actively targets MCF‐7 tumors.[25] We plan to use AR to guide nanoparticles (NPs) for precision medicine in MCF‐7 breast cancer therapy.