The most crucial discovery was that she could walk upright.

It was a crucial discovery.

This crucial discovery led him to completely redesign his furnace so that it would force high-pressure air through the molten iron using special air pumps.

Another crucial discovery was identical particles or, more generally, quantum particle statistics.

Using another crucial discovery from the wind tunnel, they made the airfoil flatter, reducing the camber (the depth of the wing's curvature divided by its chord).