An artist’ concept shows the moon of the Pluto system.

Excerpt from cbc.ca

NASA’s Pluto-bound spacecraft can now see the dwarf planet’s two tiniest known moons — both less than 30 kilometres wide.
Kerberos (which is 10 to 30 kilometres wide) and Styx (which is seven to 21 kilometres) are seen circling Pluto, along with the slightly larger moons Hydra and Nix, in an animated series of “ ” captured by the New Horizons spacecraft between 25 and May 1, and by NASA Tuesday.

Pluto and its four smallest moons can all be seen in this "family photo" captured by the New Horizons spacecraft on April 27.
space animated GIF

“New Horizons is now on the threshold of discovery,” said mission science team member John Spencer, from the Southwest Research Institute in , Colo., in a statement. “If the spacecraft observes any moons as we get closer to Pluto, they will be worlds that no one has seen before.”

New Horizons is scheduled to make a flyby of Pluto and its moons on July 14.

At the time the images were taken, the spacecraft was 89 million kilometres away. The glare from Pluto and its largest moon Charon, along with the of background stars, were damped out using processing.

Kerberos and Styx were discovered using the Hubble telescope in 2011 and 2012, respectively.