In this paper, we propose a new approach where drones attain accurate localization by fusing information from artificial lighting and their embedded inertial and barometer sensors. Our system is able to provide accurate drone localization without the use of radios, GPS or cameras. We evaluate our framework, dubbed Firefly, with a testbed consisting of four light beacons and a mini-drone. Our results show that Firefly allows locating the drone within a few decimeters of the actual position; and compared to two state-of-the-art positioning methods that rely solely on lighting information, Firefly can reduce the localization error by 50 % and 80%.. respectively.@en