MOSCOW, October 29. /TASS/. Russian cosmonauts Sergey Ryzhikov and Alexey Zubritsky - TASS's special correspondent aboard the International Space Station (ISS) - have grown perfect crystals in space for the first time in history, Russia’s state-run space corporation Roscosmos said.

Ryzhikov and Zubritsky performed their second spacewalk this year on Tuesday. During their extravehicular activity they retrieved the cassette of the Ekran-M experiment, installed on the space station’s exterior during their previous spacewalk on October 16.

"For the first time in history, perfect crystals have been grown in space," Roscosmos said.