\documentclass{article}
\usepackage{graphicx}
\usepackage{subfig}
\begin{document}
\begin{figure}[htbp]

\subfloat[Subfigure 1 caption]{\label{fig:a}\includegraphics[width=0.45\linewidth]{images/102.jpeg}}\qquad
\subfloat[Subfigure 2 caption]{\label{fig:b}\includegraphics[width=0.45\linewidth]{images/307.jpeg}}\\
\subfloat[Subfigure 3 caption]{\label{fig:c}\includegraphics[width=0.45\textwidth]{images/500.jpeg}}\qquad%
\subfloat[Subfigure 4 caption]{\label{fig:d}\includegraphics[width=0.45\textwidth]{images/404.jpeg}}%
\caption{This is a figure containing several subfigures.}

\label{fig:myfig} In the text you can refer to subfigures of figure 1 as \ref{fig:a}1a, \ref{fig:b}1b, \ref{fig:c}1c and \ref{fig:d}1d and to the sub-index as (a), (b), (c) and (d).
\end{figure}

\end{document}