* A [[Getting started#Fiji.27s_main_window|user interface]] with functions to load, display, and save images.
* Basic [http://imagej.net/docs/guide/146-29.html#toc-Section-29 image processing functionality].
* A wealth of advanced image processing [[techniques]], including [[colocalization]], [[deconvolution]], [[registration]], [[segmentation]], [[tracking]], [[visualization]] and much more.
* An extension mechanism including support for [[plugins]] and [[macros]].
ImageJ's [[extensibility]] is truly the root of its effectiveness: many advanced image-processing methods are not provided by the core application, but rather made available as third-party [[plugins]] via [[update sites]] written by specialists in the corresponding fields.