The Initial Balance
The first hour of the RTH session sets the range that everything else is measured against. Why the IB is the day's frame.
The Initial Balance is the high-low range of the first hour of regular-hours trading. ES and NQ both. It's the range early participation establishes before the rest of the market shows up.
Days that break the IB high or low set up some of the cleanest setups on the calendar — IB extensions. Days that respect both edges of the IB are rotational and want you to fade the edges, not chase.
The width of the IB matters too. A wide IB suggests volatility expansion is already happening; a narrow IB means it's coming. The market hasn't decided yet, and the break tells you when it does.
I'll go all the way into IB extension entries — the actual trigger, the stop, the sizing — in the paid course.