NBC’s One Chicago is airing its first crossover in five years tonight. Here’s how to watch the epic event featuring "Chicago Fire," 'Chicago Med," and "Chicago P.D.."

The crossover starts at 8 p.m. with "Chicago Fire" followed by "Chicago Med" at 9 p.m. and "Chicago P.D." at 10 p.m.

For the first time in five years, “Chicago Med,” “Chicago Fire” and “Chicago P.D.” are crossing over on Jan. 29. Here's how to watch the episodes and the order they're in.

T he One Chicago universe is about to experience an unprecedented crossover event, promising to be the most ambitious in the franchise's history. For the first time, on January 29