Divide the grid into some regions formed of adjacent squares, with using dominoes (1×2 black cells). Dominoes cannot overlap or touch each other by the sides. Each region must contain only the same letters and at least one letter. All the identical letters have to be in the same region.
(Rules and example from WPC 2016 IB)
History of the puzzle
Invented by Naoki Inaba (Japan) in 2010. First set of puzzles he created can be seen here.