Patient-derived explants (PDEs) still lack a unified definition. Based on a comprehensive review of multiple studies, they are defined herein as "thin slices of tissue obtained from living tissues using tissue slicing techniques that retain cellular activity, intact tissue composition, and cellular distribution characteristics”. PDEs have been in existence for many years, but they have not yet been widely used in new drug research or clinical translational studies. Efforts to improve the culture system of PDEs and integrate more analytical techniques with the PDEs have enabled the detection of more markers using fewer tissues. As an undeconstructed ex vivo model, PDEs preserve the original tissue cell types, cellular distribution, and cellular activity and feature a high establishment rate and a short detection cycle, making them suitable for drug sensitivity testing and mechanism-related studies. In particular, they show great potential in tumour-related drug sensitivity assays and immunological studies. Therefore, PDEs represent powerful ex vivo models for disease research and new drug development.