How to put a matrix in its block diagonal form (Mathematica)

[mvww]

Hello.
I got a 10x10 matrix that I know that has a block diagonal form. How can I put it in that form, using Mathematica?

Regards,
Marcus.

 

[Bill Simpson]

http://reference.wolfram.com/mathematica/ref/JordanDecomposition.html

 

[mvww]

http://reference.wolfram.com/mathematica/ref/JordanDecomposition.html

Thank you very much. :)