Total stock-based compensation expense recognized in the accompanying condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019 was as follows (in thousands):

	Three Months Ended March 31,
	2020		2019
Restricted stock units and options	$	1,066	$	883
Employee stock purchase plan		62		116
Total stock compensation expense	$	1,128	$	999

During the three months ended March 31, 2020, the Company granted 230,000 restricted stock units to employees. The restricted stock units had a weighted average grant date fair value of $1.25 per share and a primary vesting period of four years. In addition, 42,067 restricted stock units were granted to non-employee directors with a weighted average grant date fair value of $1.17. The restricted stock units awarded to non-employee directors vested immediately upon grant, but the underlying shares of common stock will not be delivered to an individual director until there is a separation of service, such as resignation, retirement or death.

During the three months ended March 31, 2020, the Company granted stock options to purchase an aggregate of 78,500 shares of common stock to certain employees at a weighted average exercise price of $1.25 per share. The options vest over a four year period. The weighted average grant date fair value was $0.93 per share, as determined using a Black-Scholes option pricing model, with the following key assumptions: risk-free interest rate of 0.79%; expected life of approximately 5.67 years; volatility of 93.83%, and dividend yield of zero.

As of March 31, 2020, there was $8.0 million of unrecognized compensation expense related to options and performance options and $0.5 million of unrecognized compensation expense related to restricted stock units. For the options that are subject to performance conditions, the Company evaluates the probability that the performance conditions will be met and estimates the service period for recognition of the associated expense.

During the three months ended March 31, 2019, the Company issued 754,729 restricted stock units to employees. Each such restricted stock award vested 100% in February 2020. The grant date fair value of the restricted stock units was $1.49 per share.

During the three months ended March 31, 2019, the Company granted certain employees stock options to purchase an aggregate of 294,900 shares of common stock at a weighted average exercise price of $1.49 per share. The options vest over a four year period. The grant date fair value of these awards was $0.3 million with a weighted average grant date fair value of $1.06 per share, as determined using a Black-Scholes option pricing model.