is it possible to insert a new element to std::set like in case of std::list for example:

//insert one element named "string" to sublist of mylist

```
std::list< std::list<string> > mylist;
mylist.push_back(std::list<string>(1, "string"));

```

Now, mylist has one element of type std::string in its sub-list of type std::list.

How can you do the same in if std::set is the sub-set of std::list my list i.e 

```
std::list<std::set <string>> mylist;

```

if you can't then why not?