Vector of vectors is currently displayed as:
(gdb) p test
$1 = std::vector of length 2, capacity 2 = {std::vector of length 2, capacity 2
= {0, 1}, std::vector of length 2, capacity 2 = {2, 3}}

while user suggested something like:
(gdb) p test
$1 = std::vector of length 2, capacity 2 = {std::vector of length 2, capacity 2
= {0, 1}, std::vector of length 2, capacity 2 = {2, 3}}
matrix contents = 
0 2
1 3

Testcase:
#include <vector>
#include <iostream>

int main(){
  std::vector< std::vector<int> > test(2, std::vector<int>(2,0));
  test[0][0]=0;
  test[0][1]=1;
  test[1][0]=2;
  test[1][1]=3;

  int a=test[1][0];
  std::cout << a;
}