“The Late Show with Stephen Colbert” marked its 100th episode on Thursday with the release of a web-only video offering a behind-the-scenes glimpse at the preparations leading up to Colbert’s debut on Sept. 8.

“A Look Back at the Beginning” runs three minutes and features documentary-style footage shot during Colbert’s run of test shows last August up through the moment he ran out on to the “Late Show” stage on Sept. 8.

By many accounts, Colbert is still finding his sea legs with “Late Show.” The show has drawn praise for its unusual mix of guests that includes prominent CEOs and noted authors and thinkers. Colbert has proven to be a sharp interviewer at times, but he also got a lot of attention earlier this week for an awkward exchange with guest Casey Affleck after a joke about Affleck’s casual attire went off the rails.

Colbert’s comedic bits have drawn mixed reviews to date. The show has yet to have a recurring franchise take off in the same way that the “Carpool Karaoke” bit has become a signature segment for Colbert’s CBS late-night companion “The Late Late Show with James Corden.”

CBS chief Leslie Moonves and other Eye execs have repeatedly voiced their support for Colbert as he settles into the chair occupied for 22 years by David Letterman. Moonves earlier this month during CBS’ fourth-quarter earnings call said that both Colbert and Corden have delivered double-digits gains in ad revenue year-over year.

For the season to date, “Late Show” is No. 2 to NBC’s “The Tonight Show Starring Jimmy Fallon” in the 11:35 p.m. time slot, averaging 0.7 in adults 18-49 and 3 million viewers for the season to date.