You'd figure that I failed trig class as for the life of me I cannot figure how to originate all scaled triangles from the same point. If polygon had an option to move base point from center to bottom left, it would be a piece of cake to draw below, but there does not seem to be an option for that. So I tried using what seemed to be right trigonometric formulas for vertix offset from center, but they did not work.
documentclass[10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}
\usetikzlibrary{shapes.misc}
\begin{document}
\begin{figure}[!htb]
\resizebox{\linewidth}{!}{
\begin{tikzpicture}
\tikzstyle{every node}=[draw,thin]
\draw[help lines] (0,0) grid (4,4);
\foreach \a in {0,...,3}{
\node[scale={\a/sin(30)},regular polygon, regular polygon sides=3]
at ({(\a)*cos(30)}, {(\a)*sin(30)}) {};
}
\end{tikzpicture}
}
\caption{Triangular grid}
\end{figure}
\end{document}

