On July 23, 2014, Company shareholders approved the Amended and Restated 2013 Equity Incentive Plan (as amended, the “Amended 2013 Plan”), which provides for the granting of stock options, restricted stock awards, restricted stock units, stock bonus awards and performance-based awards. On December 21, 2015, Company stockholders approved an amendment to the Amended 2013 Plan, increasing the number of shares that may be issued under such plan to 15,000,000 shares of common stock. The Amended 2013 Plan serves as the successor to the 2013 Equity Incentive Plan. There were no option awards under the 2013 Equity Incentive Plan. As of December 31, 2015, the Company had approximately 5,201,000 of authorized unissued shares reserved and available for issuance upon exercise and conversion of outstanding awards.

The stock options are exercisable at no less than the fair market value of the underlying shares on the date of grant, and restricted stock and restricted stock units are issued at a value not less than the fair market value of the common stock on the date of the grant. Generally, stock options awarded are vested in equal increments ranging from two to four years on the annual anniversary date on which such equity grants were awarded. The stock options generally have a maximum term of 10 years. The following table summarizes stock option activity for the Amended 2013 Plan during the years ended December 31, 2015 and 2014:

The following table summarizes unvested stock options as of December 31, 2015 and 2014:

The following table presents the weighted-average assumptions used by the Company for calculating the fair value of its employee, non-employee, officer and director stock options using the Black-Scholes valuation model that have been granted during the years ended December 31, 2015 and 2014:

The risk-free interest rates are based on the implied yield available on U.S. Treasury constant maturities with remaining terms equivalent to the respective expected terms of the options. The Company estimates the expected term for stock options awarded to employees, non-employees, officers and directors using the simplified method in accordance with Staff Accounting Bulletin 110, Certain Assumptions Used in Valuation Methods, because the Company does not have sufficient relevant historical information to develop reasonable expectations about future exercise patterns. The Company estimates the expected term for stock options awarded to employees, non-employees, officers and directors using the contractual term. Expected volatility is calculated based on the Company’s peer group, consisting of five companies in the industry in which the Company does business because the Company does not have sufficient historical volatility data. The Company will continue to use peer group volatility information until historical volatility of the Company is available to measure expected volatility for future grants. In the future, as the Company gains historical data for volatility of its own stock and the actual term over which stock options are held, expected volatility and the expected term may change, which could substantially change the grant-date fair value of future stock option awards, and, consequently, compensation of future grants.

The Company recognized expense of $5,094,791 and $7,069,833 relating to stock options for the years ended December 31, 2015 and 2014, respectively. The Company also recognized expense of $625,000 and $888,125 relating to common stock issued to employees, officers, and directors during the years ended December 31, 2015 and 2014, respectively. For the year ended December 31, 2015, stock-based compensation of $5,640,914 and $78,877, was expensed to Selling, General and Administration and Research and Development, respectively. For the year ended December 31, 2014, stock-based compensation of $7,851,685 and $64,148, was expensed to Selling, General and Administration and Research and Development, respectively. As of December 31, 2015, total unrecognized compensation cost related to non-vested stock-based compensation arrangements granted to employees, officers, and directors was $3,114,359, which is expected to be recognized over a weighted-average period of 2.22 years.