Universal Pictures

"Mostly it was about understanding ALS and what the disease is and what physical ramifications and also emotional ramifications it has on people and their families and try to learn really to decipher what Stephen's declines would have been like," Redmayne said.

Along with consulting with a choreographer and a speech therapist, he also spent hours by himself practicing Hawking's limited facial movements.

"I had on an iPad all the documentary footage I can get my mitts on and then I would wait for my girlfriend to leave the house and I would sit in front of mirror and try to get muscles working that we're not used to working," Redmayne explained.

He's diving into his starring role in the upcoming The Danish Girl with just as much intensity. Based on David Ebershoff's novel of the same name, the film is a semi-fictionalized look at the life of Einar Wegener, a Danish painter who changed her name to Lili Elbe after becoming the first man to have sexual reassignment surgery in 1931.