Some risk communication situations require helping people to visualize just how rare very rare events are. A common example occurs in prenatal genetic testing. If a couple has no other risk factors, the baseline risk of genetic diseases such as Down Syndrome is often much smaller than even 1 in 1000 (0.1%). Visually showing this ratio is challenging.
This display uses matrices of squares to represent the full probability space and a callout to reinforce how small the individual risk is.