% Author: Wikimorphism, Ika
% Date: 11/09/2014

\documentclass{amsart}
\usepackage[paperwidth=12cm, paperheight=5cm, top=0cm, left=0cm, right=0cm, bottom=0cm]{geometry}
\usepackage{amsmath,amssymb,nopageno}
\usepackage[all]{xy}
\begin{document}
\Huge
\[
	\xymatrix@C+2em@R+4em{
	\mathrm{Hom}_{\mathcal{C}}(FY,X) \ar@{=}^{\Phi_{Y,X}}[r] \ar_{\mathrm{Hom}(Fg,f)}[d] & \mathrm{Hom}_{\mathcal{D}}(Y,GX) \ar^{\mathrm{Hom}(g,Gf)}[d] \\
	\mathrm{Hom}_{\mathcal{C}}(FY',X') \ar@{=}_{\Phi_{Y',X'}}[r] & \mathrm{Hom}_{\mathcal{D}}(Y',GX')
	}
\]
\end{document}