Equity (Tables)

6 Months Ended

Jun. 30, 2014

Equity [Abstract]

Stock Options Activity

Activity with respect to the stock options is summarized as follows:

	Number  of Shares		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2014	15,375,960		$	2.46
Granted	2,475,069		7.09
Exercised	(613,659	)	1.44
Unvested options forfeited	(190,001	)	3.61
Vested options expired	(15,166	)	1.28
Outstanding at June 30, 2014	17,032,203		3.15		7.6	$	67,561,731
Vested at June 30, 2014	8,960,380		1.74		6.7	47,919,278
Vested or expected to vest at June 30, 2014 (a)	16,671,617		$	3.10	7.6	$	67,059,685

(a) Includes forfeiture adjusted unvested shares.

Stock Options Outstanding and Exercisable

Following is a summary of stock options outstanding and exercisable at June 30, 2014:

	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number outstanding	Weighted-Average Remaining Contractual Term (in years)	Weighted- Average Exercise Price		Number Exercisable	Weighted- Average Exercise Price
$0.50 - $0.76	1,066,435	4.0	$	0.67	1,066,435	$	0.67
$0.87 - $1.35	6,242,178	7.2	1.20		4,946,983	1.19
$1.40 - $2.29	1,558,368	5.6	1.64		1,393,366	1.65
$2.35 - $3.75	1,878,152	8.2	2.77		555,132	2.79
$3.95 - $5.99	3,471,401	8.9	5.14		899,135	4.99
$6.02 - $8.34	2,815,669	9.1	7.09		99,329	6.60
	17,032,203	7.6	$	3.15	8,960,380	$	1.74

Fair Value of Options, Valuation Assumptions

The assumptions used in calculating the fair value of options using the Black-Scholes-Merton option-pricing model are set forth in the following table:

	Six Months Ended June 30,
	2014	2013
Expected volatility	63.8 - 64.5%	62.15-64.27%
Expected life (in years)	5.0 - 6.0	5.5 - 6
Expected dividend yield	—	—
Risk-free interest rate	1.69% - 1.96%	0.85-1.13%

Restricted Stock Awards Roll Forward

Activity with respect to restricted stock awards is summarized as follows.  

	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2013	576,550		$5.53
Granted	489,864		7.16
Vested	(108,330	)	5.42
Forfeited	—		—
Unvested at June 30, 2014	958,084		$6.37

Allocation of Share-based Compensation

For the three and six months ended June 30, 2014 and 2013, the Company recognized stock-based compensation as follows: 

	Three Months Ended  June 30,				Six Months Ended June 30,
	2014		2013		2014		2013
Cost of sales	$	74,750	$	72,669	$	172,265	$	122,831
Research and development	162,965		122,789		322,651		198,767
Selling, general and administrative	2,528,637		1,306,989		4,643,800		2,165,641
	$	2,766,352	$	1,502,447	$	5,138,716	$	2,487,239

Summary of Warrants Outstanding

Following is a summary of the warrant activity for the six months endedJune 30, 2014:

	Number  of Warrants		Weighted-Average Exercise Price per warrant
Warrants outstanding at January 1, 2014	1,284,816		$	0.90
Warrants exercised	(1,017,000	)	0.76
Warrants outstanding at June 30, 2014	267,816		$	1.44