The icons are designed to structure the 3Rs Info Hub.

• The upper right shows the subtopic. 

in vitro | on-a-chip | in chemico | in silico | in vivo | other         -     lightbulb = course

• The lower right informs about the difficulty.  

for beginners | intermediate users | experts

• The center depicts the type of content.  

video | article | webpage | discussion | presentation

• The color indicates the R.  

replacement | reduction | refinement                                               -     exception: red = course