These are some examples of HDF version 5.0 files, the "hierarchical data format" for the management of scientific data.
HDF version 5.0 files typically have a file extension of ".h5" or ".hdf5".
IM(:,:,1) = red data;
IM(:,:,2) = green data;
IM(:,:,3) = blue data;
imwrite ( IM, 'file.hdf', 'HDF' )
.
[ X, map ] = capture ( figure_handle );
imwrite ( X, map, 'file.hdf', 'HDF' )
.
You can go up one level to the DATA page.