Equity (Tables)

9 Months Ended

Sep. 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	2,948,969		7.03
Exercised	(1,146,987	)	1.31
Unvested options forfeited	(249,670	)	4.04
Vested options expired	(84,332	)	0.81
Outstanding at September 30, 2014	16,843,940		3.32		7.5	$	64,630,326
Vested at September 30, 2014	8,987,368		1.87		6.7	47,252,742
Vested or expected to vest at September 30, 2014 (a)	16,515,621		$	3.27	7.5	$	64,242,362

(a) Includes forfeiture adjusted unvested shares.

Stock Options Outstanding and Exercisable

Following is a summary of stock options outstanding and exercisable at September 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	720,364	4.7	$	0.72	720,364	$	0.72
$0.87 - $1.35	6,102,250	6.9	1.20		4,911,058	1.19
$1.40 - $2.29	1,482,701	5.3	1.64		1,361,032	1.65
$2.33 - $3.75	1,842,320	8.0	2.77		889,298	2.69
$3.95 - $5.99	3,443,402	8.6	5.15		911,797	5.02
$6.02 - $8.34	3,252,903	9.0	7.03		193,819	6.37
	16,843,940	7.5	$	3.32	8,987,368	$	1.87

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:

	Nine Months Ended September 30,
	2014	2013
Expected volatility	63.6- 64.5%	61.41 - 64.56%
Expected life (in years)	5.0 - 6.0	6.0
Expected dividend yield	—	—
Risk-free interest rate	1.69% - 1.96%	0.85% -1.88%

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	592,864		7.05
Vested	(154,758	)	5.72
Forfeited	(720	)	7.24
Unvested at September 30, 2014	1,013,936		$6.40

Allocation of Share-based Compensation

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2014		2013		2014		2013
Cost of sales	$	70,424	$	75,287	$	242,689	$	198,119
Research and development	170,426		110,694		493,078		309,461
Selling, general and administrative	2,781,112		1,481,785		7,424,911		3,647,425
	$	3,021,962	$	1,667,766	$	8,160,678	$	4,155,005

Summary of Warrants Outstanding

Following is a summary of the warrant activity for the nine months endedSeptember 30, 2014:

	Number  of Warrants		Weighted-Average Exercise Price per warrant
Warrants outstanding at January 1, 2014	1,284,816		$	0.90
Warrants exercised	(1,079,583	)	0.80
Warrants outstanding at September 30, 2014	205,233		$	1.42