Jade Le Van created a very interesting viz with viz-in-tooltip which is based on one of her earlier endeavors. Now one single French map replaced those small multiples. Much more compact than before.

Again it picked my interest not only because of the graphics but also of the data and the context. Seems France is leaping forward to a marriage-less society. In terms of social changes, France is always leading the way.

So, I started to play with it and tweaked it a bit. And I would summarize here what I learnt by designing the viz-in-tooltip:

1.Include context in the tool tip
While the tip shows the graphical attributes of one data mark, we want to put it in the context of the entire data set, such as comparing with the aggregated results, the global average etc.

In the viz-in-tooltip, I added national average to contrast with the departmental data. Also I added the ranking relative to the other departments.
2.Minimize static content
Some text are the same from tooltip to tooltip. They do not provide additional information even though they are repeatedly used. So we don't need them so much. We should try to move them out of the tooltip, or use small font or light color to diminish their presence. The viz-in-tooltip got a small canvas. We don't want to clutter it with too much redundant stuff.

3.Highlight dynamic content
When we hover the mouse from one data mark to another to view tooltips, we are interested to view something particular to that specific data mark, something that changes from one to another, something that's dynamic.

So those content should be highlighted with big font, bright color etc. You got the idea.

4.Provide option to enlarge the viz-in-tooltip 
Obviously the viz in tooltip is small, and the small viz is not interactive. Users might want to view more details. It is a good practice to provide an option to go to a bigger chart or dashboard. The URL action filter can enable this option. The sheet is readily available.

Voila, those are my thoughts on designing the viz-in-tooltip. Please share yours if any. Click image to go to the interactive version.