Table:
|  |  | Year Ended December 31, |
| --- | --- | --- |
|  | 2019 | 2018 |
| Research and development expense: |  |  |
| Stock option awards | $8 | $38 |
| RSU awards | 13 | 27 |
|  | 21 | $65 |
| General and administrative expense: |  |  |
| Stock option awards | 12 | 61 |
| RSU awards | 105 | 104 |
|  | 117 | $165 |
| Total share-based compensation expense | 138 | $230 |
Paragraphs:
Share-based Compensation Expense
We have several share-based compensation plans covering stock options and RSUs for our employees and directors, which are described more fully in Note 11.
We measure our compensation cost related to share-based payment transactions based on fair value of the equity or liability classified instrument. For purposes of estimating the fair value of each stock option unit on the date of grant, we utilize the Black-Scholes option-pricing model. Option valuation models require the input of highly subjective assumptions including the expected volatility factor of the market price of our common stock (as determined by reviewing our historical public market closing prices). Our accounting for share-based compensation for RSUs is based on the closing market price of our common stock on the date of grant.
Our total share-based compensation expense recognized in the Company’s results of operations from non-cash and cash-portioned instruments issued to our employees and directors comprised the following (in thousands):
Question:
What are the types of share-based compensation plans?
Answer: We have several share-based compensation plans covering stock options and RSUs for our employees and directors