I have been an early employee or cofounder of three startup companies. As their in-house counsel I've been responsible for their legal matters and also handled their financial matters (accounting, tax, payroll, financial projections, etc.). I had no formal training in startup law or banking law and was required to learn both in an extremely short period of time at the first startup company.
I'm also the sole inventor of three U.S. patents (U.S. Pat. Nos. 7,357,082; 7,525,203; 8,784,172). These inventions are in the fields of electric generators, firearms, and behavioral economics. I had no formal training in any of these disciplines at the time I designed the claimed inventions.
Describe the most impressive thing you've done.