Action or movement traditionally require
into:
I ran into the bar. This is in contradistinction to the location preposition,
in:
I am drinking in the bar.
In to is two separate particles (an adverbial and an infinite marker):
I sat in to learn the details of my assignment;
I came in to warm my feet.
PS: I can also make the
to a preposition:
I went in to the jeers of my enemies.