When pressure is applied to a crystal or element which generates electricity and changes the shape of the crystal or element, the effect has occurred.

The effect you're referring to is known as the Piezoelectric effect. Here are the steps explaining how it works:

1. Pressure is applied: When a mechanical stress or pressure is applied to a piezoelectric material, it causes the material to polarize, meaning it aligns in a specific direction.

2. Polarization causes charge displacement: This polarization causes a displacement of charges within the material, creating positive and negative charges on opposite sides of the material.

3. Electric field is created: The displacement of charges creates an electric field across the material.

4. Electric potential difference is generated: This electric field leads to an electric potential difference (voltage) across the material.

5. Electricity is generated: If a circuit is connected across the material, this potential difference causes a current to flow, generating electricity.

6. Shape of the crystal changes: The applied pressure also causes a change in the shape of the piezoelectric material, which can be used in various applications such as sensors and actuators.