What is included in the XCOM: Enemy Within expansion pack?

The XCOM: Enemy Within expansion pack contains the following additional features:

• New enemies, including a deadly new organisation, EXALT, and new alien types including the Mechtoid.
• A Genetics Lab, allowing you to enhance your operatives’ abilities by augmenting their chest, brain, eyes, skin and legs.
• New weapons and armor including the Mechanized Exoskeletal Cybersuit (MEC), which can be upgraded with a grenade launcher and flamethrower.
• MELD, a valuable alien resource, which unlocks new research projects and advanced upgrades.
• Over 40 new battlefields.

NOTE: The XCOM: Enemy Within expansion pack must be purchased separately. For instructions on how to do this, see the How do I obtain XCOM: Enemy Within? point in these FAQs.