I don't think he can post a sample, Peco, because he's asking whether it's possible to do it at all. If he could show us what he wants to accomplish, it would only be by having already figured out how to accomplish it.
Officeboy, I still have a problem with the description. Since a column is vertical in nature, it's not possible to split it and then have two columns one above the other. By their nature, two columns must be to the left and right; just as it would be impossible to split a row and arrange the two rows left and right of each other.
But maybe you mean you want to split a single cell into two (so to speak) subcells, one above the other? You can do that in Word tables; maybe you're hoping to do it in Excel too?
If so, I'm going to offer the opinion that while it's practical in Word, it can never be in Excel, for the simple reason that there's no workable scheme for addressing such arrangements. You say you could split A1 into A1 and A2. Presumably the other cells on the row would remain B1, C1 and so on. But how would you refer to the second row? If "A2" now means the second subcell in the first row, how do you refer to the cell on the second row in column A? Should that cell be A3, while all the other cells on that row continue as B2, C2 and so on?
Of course not, you say; you just refer to the whole row as A3, B3, C3 and so on; and there needn't be any B2, C2 etc at all.
And in that case, you can indeed do what you want, though it's a workaround. Insert a new row after row 1. Merge cells B1 and B2, C1 and C2, D1 and D2 and so on, leaving A1 and A2 unmerged. Now you have what you're asking about (if I guessed correctly).
As for giving one cell a different width than the other cells in the same column: The objections are similar, and so is the workaround. If for presentation purposes (you wouldn't want to do this otherwise) you want to extend some cells' width into adjacent columns, you can do it—rather you can pretend to do it—by merging cells horizontally. See the attached sample. But I wouldn't call it a convenient method.
