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+# Creating a spreadsheet
+
+## The `Spreadsheet` class
+
+The `Spreadsheet` class is the core of PhpSpreadsheet. It contains
+references to the contained worksheets, document security settings and
+document meta data.
+
+To simplify the PhpSpreadsheet concept: the `Spreadsheet` class
+represents your workbook.
+
+Typically, you will create a workbook in one of two ways, either by
+loading it from a spreadsheet file, or creating it manually. A third
+option, though less commonly used, is cloning an existing workbook that
+has been created using one of the previous two methods.
+
+### Loading a Workbook from a file
+
+Details of the different spreadsheet formats supported, and the options
+available to read them into a Spreadsheet object are described fully in
+the [Reading Files](./reading-files.md) document.
+
+``` php
+$inputFileName = './sampleData/example1.xls';
+
+/** Load $inputFileName to a Spreadsheet object **/
+$spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($inputFileName);
+```
+
+### Creating a new workbook
+
+If you want to create a new workbook, rather than load one from file,
+then you simply need to instantiate it as a new Spreadsheet object.
+
+``` php
+/** Create a new Spreadsheet Object **/
+$spreadsheet = new \PhpOffice\PhpSpreadsheet\Spreadsheet();
+```
+
+A new workbook will always be created with a single worksheet.
+
+## Clearing a Workbook from memory
+
+The PhpSpreadsheet object contains cyclic references (e.g. the workbook
+is linked to the worksheets, and the worksheets are linked to their
+parent workbook) which cause problems when PHP tries to clear the
+objects from memory when they are `unset()`, or at the end of a function
+when they are in local scope. The result of this is "memory leaks",
+which can easily use a large amount of PHP's limited memory.
+
+This can only be resolved manually: if you need to unset a workbook,
+then you also need to "break" these cyclic references before doing so.
+PhpSpreadsheet provides the `disconnectWorksheets()` method for this
+purpose.
+
+``` php
+$spreadsheet->disconnectWorksheets();
+unset($spreadsheet);
+```