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**Using Interactivity to express 3D information in 2D**  The web as a publishing platform allows authors to include graphics that move. While stereoscopic  3D PDF viewing on 2D surfaces  is possible (and improving), cognition research shows that presently the best way for humans to understand 3D geometry on  a standard fully supported 2D screen is to be able to manipulate 3D perspective views dynamically, so as to simulate views created  by moving around in real space.   As is the case with video or audio, many formats are available for presenting 3D graphics online, and a good publisher should advertise which of those will be supported and migrated in the future. Also as is the case with audio/video, the present _de-facto _standard, PDF, supports 3D objects in the  Adobewithin  PDF itself. It environment. Acrobat's 3D functionality  allows for a selectable sequence of views of embedded 3D objects, in which each view can have a subset of objects visible from a given vantage point. As the The first interactive 3D PDF was published in a major joural (_Nature_) in 2009 Nature\cite{2009Natur.457...63G}, and a limited number others have appeared in major scientific publiscations since \cite[e.g.][]{2012ARA&A..50..491P}.  The  tools for creating _creating_  3D PDFs were spun off from Adobe itself a few years ago, so presently,  it had become somewhat can be  cumbersome to generate such figures. A [tutorial](http://www.astrobetter.com/tutorial-for-embedding-3d-interactive-graphics-into-pdf/) now exists that allows a user to generate a PDF with a 3D figure using LaTeX tools. PDF has the advantage of offering a printable equivalent of an onscreen document, but it is not clear for how much longer a printable version take precedence over intereactive features.  Nature figure screen shots from \cite{2009Natur.457...63G} see also \cite{2012ARA&A..50..491P}.