def _process(json_data):
    """Return a 3d array (iteration x spreadsheet) of microplates' names."""

    iterations = []
    for iteration in json_data[u'iterations']:

        spreadsheets = []
        for spreadsheet in iteration[u'spreadsheets']:
            spreadsheets.append(spreadsheet[u'microplates'].keys())

        iterations.append(spreadsheets)

    return iterations