Not guaranteed. If you exercise your options at company X, say $20 per share, left company X, and company Y buys company X for $10 per share, then you just lost

Not guaranteed. If you exercise your options at company X, say $20 per share, left company X, and company Y buys company X for $10 per share, then you just lost money. I imagine this is pretty rare but it's possible for a company to acquire another and strictly buy all preferred stock instead of common stock and then all employees get nothing [0]. [0] This happened to a friend of mine where all execs had preferred stock and were totally fine selling the company and screwing over the employees. Make sure your founders/execs have common stock so that everyone is on the same playing field...