What are the types of focus areas in mechanical engineering?

What are the different branches of mechanical engineering that people focus on.  Both from the academic perspective and the professoinal and / or research perspective.  Mechanical engineering is a broad field, and I am curious about what specific focus areas exist.

If you are planning to reside / work in Middleast. Then Out of Vast scopes of Mechanical Engineering is the Thermodynamics. which leads you to HVAC (Heating Ventilating and Air-Conditioning) Services. HVAC application itself is having loads of scopes. such as , Design, Maintenance, Supervision, Installation and Commissioning. Out of these four catagories. You can have handsome package if you choose one of those.