Logarithmic spiral with directional arrows. Visual example of a parametric curve in topology. From Sarmate's technical TikZ gallery (sources: MartinThoma/LaTeX-examples MIT, TeXample.net LPPL) — see also our 900+ figures on /tikz-gallery.php.
% Thanks to Jake: http://tex.stackexchange.com/a/142815/5645
\documentclass[border=5pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}
\draw [red] (0,0) circle [radius=1];
\draw [domain=1:18.8,variable=\t,smooth,samples=200,->,>=stealth']
plot ({\t r}: {1+2*exp(-0.1*\t)});
\end{tikzpicture}
\end{document}
