In a zooming user interface directories and programs are not present within windows but are placed instead (in vectorial form) directly on an infinite virtual desktop. A user navigates through the virtual space by panning left to right and up and down, as when one uses a video camera, and by zooming into objects of interest, as when one uses the zoom function in a video camera. At one point in the zooming process an object of interest can look like a small speck, at another point it can look like a thumbnail of a page of text, and at still another point it can look like a normal size page of text or a magnification of a page of text.
Most research groups working on ZUIs are generating Open source systems and applications and using open source tools to do so. The longest running effort has been over the Pad++ project started by Ken Perlin at New York university and continued at the Human Computer Interface Lab at the University of Maryland. The efforts surrounding the Pad++ project are however a combination of open source and proprietary standards. The most recent effort has been by Jef Raskin, who undertook the incarnation of his concepts of a humane interface by using open source elements only, within his rendition of a ZUI.
The ZUI is the new interface paradigm which is receiving the most work by the biggest variety of researchers in the contest to come up with a flexible and realistic successor to the traditional windowing GUI. But since the total amount of investment in building a successor to the present GUI is rather small, the effort in developping ZUIs is proportionately humble. Each year hundreds of millions of Euros are spent on making small changes on existing GUIs (in desktop format or within Web delivery), while a much smaller amount is spent on significantly new interfaces and a smaller one still is spent on developping ZUIs.