Know Little Bit about remaining things.

So, in that T concept, there should be your knowledge in one thing in depth but you know little bit of others too only then you will become successful. 

It is because in life there are so many things which are changing that if you don't know about the remaining things then you won't be able to connect & you won't become an interesting person.

That one thing which you know about in-depth maybe that will become irrelevant. So, its important to do it.