That 'something' inside the cube is a secret that only Molyneux himself, and perhaps his development team at 22 Cans, know. What’s more important, it’s something that only the person who picks at the last cube will be able to discover. In other words, of the thousands of people playing the game, only one can 'win'.
All that is known about what the person who picks the last cube will find is that it’s something that, in Molyneux's own words, 'will change his life forever'.
Now, to get to the center of the enormous cube, made up of thousands of millions of smaller cubes, you’ll have to spend many hours picking away at it. The process is very simple: for every time you touch the screen you'll pick away one cube and win a coin, and if you do it in rhythm you'll win more coins. This way, as you get more coins you'll be able to buy more objects, such as bombs or picks of different materials that'll make you pick faster.
Curiosity is a very peculiar experiment. It doesn’t provide direct entertainment, as other Android games do, but it definitely offers something different. If it is ultimately worth it is something that only time, and the winner, will tell.