Item

Item[expr_, opts___]

represents an item within constructs such Grid

It modifies on outer container applying custom styles specified in opts

Grid[{{Item[a, Frame -> True], b}, {c, d}}]

Another example

a = {{1, 2}, {3, 4}};
Grid[KroneckerProduct[IdentityMatrix[5], a]] /. {0 -> 0, 
   x_?NumberQ -> Item[x, Background -> Orange]}

Options

The same as for Style