Lensless fiber endomicroscopy represents a transformative approach in biomedical imaging, enabling high-resolution, minimally-invasive optical imaging and targeted light delivery. This technology leverages holographic detection and wavefront correction to achieve three-dimensional imaging in an extremely compact form factor, making it ideal for applications such as brain surgery. The review highlights recent advancements in lensless fiber endomicroscopy, focusing on multimode and multicore fibers, and discusses their potential for real-world applications. It also identifies challenges in translating these innovations into clinical practice, including issues with signal-to-noise ratio, resolution, and the need for advanced computational methods. Lensless fiber endomicroscopes use optical fibers as waveguides for both light delivery and detection, allowing external placement of light sources and detectors, which reduces the probe's footprint. This technology enables dynamic in vivo imaging, providing real-time insights into cellular and subcellular processes. It also supports controlled light delivery, enabling optical excitation, nonlinear contrast mechanisms, optogenetic stimulation, optical manipulation, and photo-therapy, which could revolutionize early disease detection, targeted biopsies, and treatment monitoring. The review discusses the potential of lensless fiber endomicroscopy in various biomedical applications, including cancer detection, neuroimaging, and optogenetics. It also addresses the challenges in translating these technologies into clinical settings, such as the need for improved signal-to-noise ratios and the development of more robust fiber designs. The integration of advanced computational methods, such as deep learning, and innovative fiber designs, such as 3D-printed diffractive optical elements, is highlighted as a path to overcoming these challenges. The review emphasizes the importance of balancing innovation with practical implementation, ensuring that these technologies are user-friendly, cost-effective, and compatible with existing medical workflows. As the field progresses, the potential for lensless fiber endomicroscopy to revolutionize medical imaging and treatment is significant, offering new possibilities for minimally invasive diagnostics and therapies. The review concludes that continued collaboration between researchers, clinicians, and industry is essential for translating these advancements into practical clinical applications.Lensless fiber endomicroscopy represents a transformative approach in biomedical imaging, enabling high-resolution, minimally-invasive optical imaging and targeted light delivery. This technology leverages holographic detection and wavefront correction to achieve three-dimensional imaging in an extremely compact form factor, making it ideal for applications such as brain surgery. The review highlights recent advancements in lensless fiber endomicroscopy, focusing on multimode and multicore fibers, and discusses their potential for real-world applications. It also identifies challenges in translating these innovations into clinical practice, including issues with signal-to-noise ratio, resolution, and the need for advanced computational methods. Lensless fiber endomicroscopes use optical fibers as waveguides for both light delivery and detection, allowing external placement of light sources and detectors, which reduces the probe's footprint. This technology enables dynamic in vivo imaging, providing real-time insights into cellular and subcellular processes. It also supports controlled light delivery, enabling optical excitation, nonlinear contrast mechanisms, optogenetic stimulation, optical manipulation, and photo-therapy, which could revolutionize early disease detection, targeted biopsies, and treatment monitoring. The review discusses the potential of lensless fiber endomicroscopy in various biomedical applications, including cancer detection, neuroimaging, and optogenetics. It also addresses the challenges in translating these technologies into clinical settings, such as the need for improved signal-to-noise ratios and the development of more robust fiber designs. The integration of advanced computational methods, such as deep learning, and innovative fiber designs, such as 3D-printed diffractive optical elements, is highlighted as a path to overcoming these challenges. The review emphasizes the importance of balancing innovation with practical implementation, ensuring that these technologies are user-friendly, cost-effective, and compatible with existing medical workflows. As the field progresses, the potential for lensless fiber endomicroscopy to revolutionize medical imaging and treatment is significant, offering new possibilities for minimally invasive diagnostics and therapies. The review concludes that continued collaboration between researchers, clinicians, and industry is essential for translating these advancements into practical clinical applications.