How did they make the 45mm 1.8 Olympus so small?

Someone sat down and concentrated again and again on how to make it properly compact and cleverly shaped while being both sharp wide-open and of very fast focus.

They got my money and I almost NEVER buy these things new!

I do belive a lot of the previous m4/3rds lenses are nowhere near as small as they could have been, just see the new Lumix 14-42 kit zoom coming out.