I have a brand-new favicon at this blog. It is actually a very simple, albeit special, smiley (or “emoji,” of you prefer):

The first model-theoretic smiley!

Modley is, as most of you have already noticed, the “consequence” or “satisfaction” symbol used in model theory and in Logic in general, rotated 90° counterclockwise. You may typeset the actual symbol $\models$ in $\LaTeX$ by using \models in math mode.

One can metaphorically say that the sole introduction of this symbol signals the beginning of modern mathematical logic, since it works as the bounds between mathematical structures (on the left) and the language in which we write their properties (on the right).