They have eight suckered arms and two tentacles and are generally quite small (typical male mantle length being between 1 and 8 cm (0.39 and 3.15 in)).

The organ contains filters which may alter the wavelength of luminescence closer to that of downwelling moonlight and starlight; a lens with biochemical similarities to the squid's eye to diffuse the bacterial luminescence; and a reflector which directs the light ventrally.

[2] Sepiolida are iteroparous and a female might lay several clutches, each of 1–400 eggs (dependent on species), over her estimated one-year-long lifetime.

[2] Symbiosis with A. fischeri from the surrounding seawater is initiated immediately upon hatching, and the bacteria's colonisation of the juvenile light-organ induces morphological changes in the squid that lead to maturity.

Sepiolid taxonomy within the coleoid cephalopods is currently controversial, thus their position is subject to future change.