Fiji is an image processing package. It can be described as a distribution of ImageJ together with Java, Java 3D, and a lot of plugins organized into a coherent menu structure. Fiji compares to ImageJ as Ubuntu compares to Linux. The main focus of Fiji is to assist research in life sciences. For users, Fiji is easy to install and has an automatic update function, bundles a lot of plugins and offers comprehensive documentation. Developers may access the source code of all internals, libraries, and plugins, which eases the development and scripting of plugins.