Writing polynomials in standard form in a matrix

A symbolic matrix with two parameters, say $x,y$, shows up in my calculation. The entries of the matrix are homogeneous polynomials. I want the entries to be written in some standard format, e.g. in ascending power of say $x$ and descending powers of $y$, or vice versa. But Mathematica insists on factoring some of them. How do you force Mathematica to expand expressions such as $ab^2(a^2-b^2)$ or $a(a^2-b^2)^2$ that occur inside a matrix?

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Closely related: How to keep Collect result in order?. –  Artes Jan 13 at 21:59
Just to elaborate on Artes' answer, you can do something like this: Collect[2*a^3*(a + 2 b)^2, a] –  Vincent Tjeng Jan 14 at 16:59
@Artes thanks. It looks like my problem was that I was using Collect[MatrixForm ... instead of MatrixForm[Collect ... Somehow the first one does not work but the second one does! –  Maesumi Jan 14 at 18:00