The top of a product tree must be a product configuration.
Create a product to represent the work the team is focused on. A product can be as large as a car or as small as a mechanical heart valve. In this example, the product tree starts at the product level, such as Automated Meter Reader.

The product manager or team lead might then add child products (for example, Handheld Reader, Reader Probe), under Automated Meter Reader to further organize the product. The product manager or team lead might add a group of child products from other models, such as Current Measurement, Voltage Measurement, and Tampering Measurement. In this example, the child products are all measurements. The measurements could be grouped under a configuration called Measurement or could be placed individually as products under Automated Meter Reader. If placed as products, the dimensions and values for the products must match the dimensions and values set on the parent configuration.
Further, product trees can be organized at multiple levels, for example, by model or by year. Meter Reader might be one of several meter readers that resides in a group of products called Model Year 2017. The products can also be reused as child products to populate other products. For example, the Measurement product could be a child product of several groups of products, such as Model Year 2015, Model Year 2016, and Model Year 2017.
You can add a child product to a product or configuration as many times as you need to add it. See Reusing products and configurations.