I am trying to align node text to left but it seems below code still put the text at the center of node:
\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[thick]
\node[draw,rectangle,minimum width=10em,align=left] (A) {Abc};
\end{tikzpicture}
\end{document}
The output is:

Update: Thanks for your valuable comments, so I should update it as following:
\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[thick]
\node[draw,rectangle,minimum height=4em,text width=10em,align=left] (A) {Abc};
\end{tikzpicture}
\end{document}
Then it's exactly what I want:

text widthfor the text boxes, minimum width is for the shape. – percusse Aug 19 '14 at 03:23minimum height=2cm. – percusse Aug 19 '14 at 03:32