Note 9. Stock Options

The following table summarizes the outstanding stock option activity during the periods indicated:

	Number of shares			Weighted average exercise price		Weighted average remaining contractual term
Balance at December 31, 2015		756,692			2.10		7.60
Granted		359,319			2.60		9.40
Exercised		(58,155	)		2.36		3.50
Expired/Forefeited		(17,469	)		2.13		2.60
Balance at December 31, 2016		1,040,387			2.25		7.80
Granted		4,995		15.85			9.80
Exercised		(155,520	)	2.08			6.05
Balance at March 31, 2017		889,862		2.36		7.82
Vested and exercisable at March 31, 2017		494,408		2.07		7.01
Vested and expected to vest at March 31, 2017		889,862		2.36		7.82

The weighted average grant-date fair value of options granted during the three months ended March 31, 2017 and for the year ended December 31, 2016 was $6.21 and $1.23, respectively. For fully vested stock options, the aggregate intrinsic value as of March 31, 2017 and December 31, 2016 was $6,470,698 and $7,770,086, respectively. For stock options expected to vest, the aggregate intrinsic value as of March 31, 2017 and December 31, 2016 was $4,942,466 and $4,569,243, respectively.

During the year ended December 31, 2016, a total of 57,475 shares of restricted common stock with a fair value of $2.00 per share were issued to the Company’s Chief Financial Officer and Chief Operating Officer of which 100% of the shares vest six months after the completion of an initial public offering. The shares vested in February 2017. The Company recorded $53,056 and $61,894 in expense associated with these shares during the three months ended March 31, 2017 and the year ended December 31, 2016, respectively.

At March 31, 2017 and December 31, 2016 there was $471,071 and $522,818, respectively, of total unrecognized compensation cost related to unvested stock options and restricted stock granted under the plans. These costs are expected to be recognized over the next three years and is based on the date the options were granted.

The Company currently uses authorized and unissued shares to satisfy share award exercises.