Market Mechanics: From the open to close

What is your opinion, theory, or whatever you want to call it of what takes place on a day-to-day basis in markets from the open to the close. I'm not referring to the obvious general answer of "buying and selling" or supply/demand. I'm well aware of those things.

Clearly you either get activity that's going to be ranging or trending, but more specifically I'm referring to what is going on for the first 15-30mins of the opening bell with all of those market orders and liquidity and then once again once we get towards the final 15-20mins.

I think this kind of information is very pertinent to traders. Do they know what they're actually looking at as that morning liquidity comes into a stock or instrument and how to gameplan around it?

I hope I make sense in what I'm asking.