This property enables you to specify a level of transparency for the form and its controls. This property differs from transparency provided by the TransparencyKey which only makes a form and its controls completely transparent if they are the same color as the value specified in the TransparencyKey property. When this property is set to a value less than 100% (1.00), the entire form, including borders, is made more transparent. Setting this property to a value of 0% (0.00) makes the form completely invisible. You can use this property to provide different levels of transparency or to provide effects such as phasing a form in or out of view. For example, you can phase a form into view by setting the Opacity property to a value of 0% (0.00) and gradually increasing the value until it reaches 100% (1.00).