Loading Controller from another Controller

[eluser]drakeonfire[/eluser]
Hello,

Title kinda says what I need to do.

For example I have controller "main", which also has a routing function in (to determine where certain things need to go), and it may need to go to product or blog controller etc, how can I do this?

If I can make one request - please do not try and question the logic behind the routing function, as there is good reasoning for it, I can assure you.

Thank you!