employees may choose not to exercise their options if the market value of the shares is below the strike price. employees may exercise their options by paying the strike price to the employer anytime between the vesting and expiration dates. employees may purchase the stock on the grant date, but can not sell their shares until the vesting date. if the market price is below the strike price, the employee may purchase the stock at fmv and sell it to the company for the option price. the employee will receive the stock on the vesting date without having to pay for it.