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, 2018		1,407,049		$	8.73		8.1
Granted		395,485			11.39		9.5
Exercised		(77,994	)		2.96		4.5
Expired/Forfeited		(63,891	)		11.19		0.1
Balance at March 31, 2019		1,660,649		$	9.54		8.3
Vested and exercisable at March 31, 2019		645,179		$	7.97		7.2
Vested and expected to vest at March 31, 2019		1,660,649		$	9.54		8.3

The weighted average grant date fair value of options granted during the three months ended March 31, 2019 and for the year ended December 31, 2018 was $4.00 and $3.97, respectively. For fully vested stock options, the aggregate intrinsic value as of March 31, 2019 and December 31, 2018 was $3,431,528 and $2,485,258, respectively. For stock options expected to vest, the aggregate intrinsic value as of March 31, 2019 and December 31, 2018 was $2,594,538 and $993,372, respectively.

At March 31, 2019 and December 31, 2018, there was $4,848,962 and $2,781,062, respectively, of total unrecognized compensation cost related to unvested stock options granted under the Company’s equity plans. That cost is expected to be recognized over the next three years and is based on the date the options were granted.

During the three months ended March 31, 2019, the Company granted 95,478 Restricted Stock Units (RSUs) at a weighted average grant date fair value of $11.35 per share. No RSUs vested during the three months ended March 31, 2019. As of March 31, 2019, the Company has 99,440 RSUs outstanding at a weighted average grant date fair value of $11.41 per share and a weighted average remaining contractual term of 3.7 years. As of March 31, 2019, there was $1,081,000 of total unrecognized compensation cost related to unvested RSUs.

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