3D Slicer is a free, open-source software package for medical image analysis and visualization. It provides an interactive environment for medical image segmentation, volume rendering, registration, and quantitative analysis. 3D Slicer supports the development of algorithms for image analysis, enabling users to visualize and analyze medical images from multiple sources, such as CT, MRI, ultrasound, and microscopy. It is a powerful tool for medical researchers and clinicians, allowing them to explore and analyze data in three dimensions.