British astronaut Tim Peake and two colleagues have been welcomed aboard the International Space Station after a six-hour journey from Kazakhstan.
No Brit has undertaken such a mission - or even left Earth - in more than two decades.
Mr Peake will be onboard the ISS for six months.
Tim Peake will undergo 10 gruelling exercise sessions each week while he is on the International Space Station to maintain his strength, bones and fitness.
The British astronaut will spend two hours a day working out in 23C heat on an exercise bike, treadmill and specially-designed weights machine.
A lack of gravity means that heat will not dissipate from Peake's body, causing him to get "pretty warm" during a workout.
His exercise programme will be reviewed each week by a specialist watching him from Earth.
Dr Jon Scott, who helped Peake prepare for life in space, said: "Exercise is one of the best counter-measures we have against all the changes that will take place in his body, so he needs to be ready to exercise almost as soon as he arrives on ISS.
"Bones are very susceptible to becoming thinner and weaker in space."
The parents of British astronaut Tim Peake missed a phone call from their son made from the deck of the International Space Station.
British astronaut Tim Peake has tweeted his first picture of his view from the International Space Station (ISS).
British astronaut Tim Peake may have only been in space for three days, but he has already been busy.