Suppose I have a matrix 'mat' as
mat = Table[Subscript[m, i, j], {i, 5}, {j, 5}];
mat // MatrixForm
I want to extract the first column (or any row) as
a = mat[[All, 1]]
{Subscript[m, 1, 1], Subscript[m, 2, 1], Subscript[m, 3, 1], \
Subscript[m, 4, 1], Subscript[m, 5, 1]}
But I want the output as
{{Subscript[m, 1, 1]}, {Subscript[m, 2, 1]}, {Subscript[m, 3,
1]}, {Subscript[m, 4, 1]}, {Subscript[m, 5, 1]}}
How can I do that?