From the number of daily sunrises to preparing a cup of coffee, living in microgravity about 250 miles above the Earth is remarkably different from terrestrial life.
Scott Kelly, who recently wrapped up a 340-day mission aboard the International Space Station, is among the rare few who understands this well.
"I've been up here for a really long time and sometimes, when I think about it, I feel like I've lived my whole life up here," Kelly told CNN on Tuesday.
While the year in space wasn't Kelly's first (he's been on a total of four missions), it was his longest -- and longer than any other American astronaut. It will take time for him to re-acclimate, both physically and mentally, to life back on Earth.
Below, a look at five ways Kelly must readjust -- for better or worse -- after his extended stay in space.