A flame generated in space for the BASS-II combustion experiment on the International Space Station.
ESA astronaut Alexander Gerst posted this photo on Twitter, commenting: "This is a flame we generated in space. It helps to increase fire safety on Earth."
More about BASS: http://spaceflightsystems.grc.nasa.gov/SOPO/ICHO/IRP/MSG/BASS/
More ISS science: http://www.esa.int/Our_Activities/Human_Spaceflight/Blue_dot/Space_Station_Science