Brainchild = someone’s idea or invention, especially if successful.

• This festival celebration was the brainchild of the Corporation mayor.
• The project was the brainchild of a student.
• This dance sequence is the brainchild of the assistant director.
• This method of cultivation is the brainchild of the new agriculture minister.

.

Brain drain =a movement of a large number of highly skilled or professional people from the country where they were trained to other countries where they can earn more money.

• The government has done nothing to stop the brain drain as more and more professionals are moving to different countries.
• Many see the brain drain as bad for the Indian economy.
• Britain has suffered a huge brain drain in recent years.