26.

Rapidly flapping wings to hover, dive, climb, or dart through an open doorway,
DARPA’s remotely controlled Nano Air Vehicle relays real-time video
from a tiny on-board camera back to its operator.
Weighing less than a AA battery and resembling a live hummingbird,
the vehicle could give war fighters an unobtrusive view of threats inside
or outside a building from a safe distance.
source: DARPA