Vector Method Push_back - call by value not reference

//push_back method - call by value not reference

/*
* Code to explain the issue
* Followed by modified version of same code , to meet my requirements
*/
vector<vector<string> > outerVector;
vector<string> innerVector;
cout << "Inner Vector Address:  " << &innerVector<< endl;//Inner Vector Address:  0x28febc
outerVector.push_back(innerVector);

string one = "one";
string two ="two";

vector<string> lastElement = outerVector.back();
cout << "OuterVector LastElement Address: " << &outerVector.back() << endl;//OuterVector LastElement Address: 0x3d2238
lastElement.push_back(one);
cout << "lastElement Size: " << lastElement.size()<< endl;//lastElement Size: 1

lastElement = outerVector.back();
cout << "OuterVector LastElement Address: " << &outerVector.back() << endl;//OuterVector LastElement Address: 0x3d2238
lastElement.push_back(two);
cout << "lastElement Size: " << lastElement.size() << endl;//lastElement Size: 1


/*
* In the below code
* I modified the above code to support reference for the inner elements
*/
//Store the address in inner vector to access the original element
vector<vector<string>*> outerVector;
vector<string>* innerVector = new vector<string>;
cout << "Inner Vector Address:  " << innerVector<< endl;//Inner Vector Address:  0x762238
outerVector.push_back(innerVector);

string one = "one";
string two ="two";

vector<string>* lastElement = outerVector.back();
cout << "OuterVector LastElement Address: " << outerVector.back() << endl;//OuterVector LastElement Address: 0x762238
lastElement->push_back(one);
cout << "lastElement Size: " << lastElement->size()<< endl;//lastElement Size: 1

lastElement = outerVector.back();
cout << "OuterVector LastElement Address: " << outerVector.back() << endl;//OuterVector LastElement Address: 0x762238
lastElement->push_back(two);
cout << "lastElement Size: " << lastElement->size() << endl;//lastElement Size: 2