"is the photography just a perfect timing ??"

No Olivier, I don't believe it is, however timing is a a major part. In essence it is a captured moment that can be kept and shown again, but to make it have meaning and significance it has to say something, which is where composition and subject come into play.

To quote :
"To take a photograph means to recognize – simultaneously and within a fraction of a second– both the fact itself and the rigorous organisation of visually perceived forms that give it meaning."

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html