Two years after covering the career and life of Jackie Robinson, Ken Burns will devote another of his acclaimed documentaries to an iconic figure in sports. On Wednesday, PBS announced that Burns will produce and direct a two-part, four-hour documentary on Muhammad Ali.

Production on the project actually began last year, with Burns once again sharing directing and producing duties with Sarah Burns and David McMahon, with whom he collaborated on 2016’s Jackie Robinson film and 2013’s The Central Park Five. The Ali documentary is expected to be ready for broadcast on PBS in 2021.

Burns has often celebrated sports figures who were historically and culturally significant, especially in fighting against social injustice, in his films. No athlete made more of an impact during his time than Ali, as the filmmaker said in an official statement announcing the film.

“Muhammad Ali may be the most iconic figure of the 20th century. He arrived at exactly the right moment, amidst the tumult and upheaval of the 1960s, and he shaped his times with his powerful voice, mesmerizing presence, and achievements in the ring. But beyond the astonishing athletic gifts and mountain of charisma, there’s a very complex, dynamic man whose life story has yet to receive the comprehensive treatment it deserves.”

Several documentaries and dramatizations have been made about different parts of his life, whether covering fights against Sonny Liston, George Foreman and Larry Holmes or his conscientious objection to the Vietnam War. There has even been a film about Ali in which he didn’t even appear . HBO also has an Ali documentary in development , a multi-part project directed by Antoine Fuqua and produced by LeBron James.

Sarah Burns noted the larger territory that their film needed to address in order to suitably cover Ali’s life.

“Muhammad Ali’s passing last year gave us reason to celebrate his boxing feats as well as his contributions as an ambassador for human rights, and as a voice and symbol of pacifism. But it’s easy to forget how divisive a figure he was, proudly associating with the Nation of Islam, refusing induction into the Army before the Vietnam War had become deeply unpopular. “We’re eager to get beyond the archetypes and examine who and what influenced his choices, and how he maintained the courage of his convictions when those choices seemed to go against the tide.”

Considering the length and depth of Ali’s life as a boxer, activist and cultural figure, four hours seems a bit short for a Burns documentary. After all, we’re talking about a filmmaker who devoted nearly 19 hours apiece to Baseball, Jazz and more than 10 to The Civil War. He’s known for his long-form, multi-part films. His upcoming documentary on The Vietnam War will be another 10-part, 18-hour epic, set to air in September.

However, Burns’s Robinson film was also four hours (aired in two parts on PBS) and his documentaries that focus on a single subject, rather than an entire era, tend to be shorter.

[Deadline]