Uznański was born in Łódź, Polish People's Republic on 12 April, 1984 – the 23rd anniversary of Yuri Gagarin's first human orbital spaceflight.

[3] In 2011, he received a doctor's degree with distinction from the University of the Mediterranean Aix-Marseille II for thesis on radiation-tolerant designs for space applications.

[5] In an interview, Uznański revealed that Mirosław Hermaszewski (Poland's first cosmonaut) supported him throughout the process and was the first person to call him with congratulations on the morning after he was selected.

[2] In August 2023, Poland's Development and Technology Minister, Waldemar Buda, announced that a Polish astronaut would fly to the International Space Station (ISS) in 2024, adding that if the mission went ahead Poland would submit the candidature of Uznański, which in turn would have to be approved by the ESA and the American company Axiom Space.

[6] He joined the ESA to undergo his training for Axiom Mission 4 on 1 September 2023,[7] which is currently expected to launch no earlier than April 2025.