The Centipede Project acquired the specs of the Night-Night Gun designed by Agents Leo Fitz and Jemma Simmons through their infiltration within S.H.I.E.L.D.'s ranks as part of HYDRA, following their multiple encounters with Phil Coulson and his team.
The Dendrotoxin Grenade releases an airborne modified version of the dentrotoxin used in the bullets that renders the targets within its area of effect in a state of unconsciousness that seems as if time has not passed since the explosion of the grenade.
One such grenade was thrown towards Phil Coulson and Grant Ward in order to delay them for capture after they jumped from a train where Cybertek hired mercenaries were pursuing them. When they awakened from the effects of the grenade, Coulson and Ward thought the train had teleported away. Coulson then procured the grenade and took it aboard the Bus to have its specifications downloaded to S.H.I.E.L.D. Headquarters.