Note 7 - Stockholders' Equity - Option Activity for Stock Option Plans (Details)	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares
Outstanding, options (in shares) | shares	291,807
Outstanding, weighted average exercise price, options (in dollars per share) | $ / shares	$ 13.96
Granted, options (in shares) | shares	605,500
Granted, weighted average exercise price, options (in dollars per share) | $ / shares	$ 5.94
Forfeited, options (in shares) | shares	(3,958)
Forfeited, weighted average exercise price, options (in dollars per share) | $ / shares	$ 3.74
Outstanding, options (in shares) | shares	893,349
Outstanding, weighted average exercise price, options (in dollars per share) | $ / shares	$ 8.57
Outstanding, weighted average remaining contractual life, options (Year)	9 years 91 days
Outstanding, aggregate intrinsic value, options | $	$ 514,200
Vested and expected to vest, options (in shares) | shares	539,272
Vested and expected to vest, weighted average exercise price, options (in dollars per share) | $ / shares	$ 10.07
Vested and expected to vest, weighted average remaining contractual life, options (Year)	8 years 350 days
Vested and expected to vest, aggregate intrinsic value, options | $	$ 402,783
Exercisable, options (in shares) | shares	183,824
Exercisable, weighted average exercise price, options (in dollars per share) | $ / shares	$ 17.07
Exercisable, weighted average remaining contractual life, options (Year)	7 years 335 days
Exercisable, aggregate intrinsic value, options | $	$ 213,047