Aging is a systemic biological process that spans multiple levels, including molecules, cells, tissues, and organs. Cellular senescence is regarded as one of the key mechanisms driving functional decline, chronic inflammation, and the onset and progression of age‐related diseases. Among the numerous biomarkers of senescence, senescence‐associated β‐galactosidase (SA‐β‐gal) has become one of the most widely used classical indicators in cellular senescence research. However, conventional X‐gal staining and lysate‐based assays largely rely on endpoint, ex vivo, or semi‐quantitative readouts, making it difficult to meet the growing demand for real‐time, in situ, dynamic, and highly sensitive visualization of senescent states in live cells, tissue sections, and living organisms. The development of fluorescence imaging technologies, particularly near‐infrared fluorescence imaging, has provided a new toolkit for detecting SA‐β‐gal activity. Fluorescent probes containing a β‐D‐galactose unit can be activated by β‐galactosidase, resulting in the recovery or change of fluorescence signals. This review systematically summarizes recent advances in senescence imaging targeting SA‐β‐gal, including turn‐on probes, ratiometric probes, AIE‐based probes, and nanoprobes. In particular, we highlight strategies to improve the specificity of SA‐β‐gal imaging, enhance the ability to distinguish SA‐β‐gal activity in senescent cells from that in non‐senescent tumor cells, and further discuss the challenges and opportunities in this field.

Cellular‐mesenchymal epithelial transition factor (c‐Met), a receptor tyrosine kinase, participates in various human physiological processes, including cell proliferation, embryonic development, and tissue regeneration via the hepatocyte growth factor (HGF)/c‐Met signaling pathway. Abnormal activation of this pathway is associated with tumor growth and treatment resistance. Previous work has demonstrated that c‐Met is overexpressed in various solid tumors, making it a potential therapeutic target. The development of diagnostic and therapeutic agents targeting c‐Met is also of considerable interest. In this review, we provide an overview of the current progress with c‐Met‐targeted probes that use HGF ligands, antibodies, peptides, and small molecules for noninvasive imaging with techniques such as MRI, PET, SPECT, and optical imaging. We also summarize the design strategies and imaging effects used for tumor diagnosis. Through these insights, we aim to facilitate the further advancement of novel c‐Met‐targeted imaging agents, thereby enhancing the precision of tumor diagnosis and evaluation of drug efficacy.

Molecular imaging plays important roles in many fields, including disease diagnosis, therapeutic efficacy evaluation, intraoperative imaging guidance, drug metabolism monitoring, and patient selection for appropriate treatment. As a key component, the targeting ligand determines the specificity, affinity, and in vivo performance of molecular imaging probes. In this review, high‐throughput screening and biological display platforms for the discovery of ligands applicable to molecular imaging are briefly reviewed. Basic information on ligand development for molecular imaging is first introduced, followed by a presentation of various selection platforms and typical or iterative cases. The features, advantages, limitations, and application scope of screening and display platforms are compared and discussed. Last, a basic selection strategy and a perspective for protein‐based ligands are provided.