The Similar products by sale web part displays N products which other customers buy with the chosen product most commonly. By default, four products are displayed at the most. For instance, if a customer has bought product A together with products B and C, some other customer who is viewing the details of product A is being displayed also with products B and C. This is because products B and C were purchased together with product A by the first customer.

You can find an example of control nesting in Using nested controls.

Help URL: http://devnet.kentico.com/docs/webparts/index.html?SimilarProductsBySale_overview.htm