Agents of S.H.I.E.L.D. reached their 50 episode milestone last week, and we’re looking back at the five best episodes from the story so far.

The cast and crew of Agents of S.H.I.E.L.D. celebrated the milestone in a recent video from Marvel, looking back on favorite moments and remembering their adventures together.

While the team recalls their fondest memories, we’re looking back on the five best episodes that have made Agents of S.H.I.E.L.D. such a heart-pounding journey.

1×06 – ‘F.Z.Z.T.’

Many fans (and many, many critics) found a lot to complain about in Agents of S.H.I.E.L.D.‘s first season, but even early on, the series showed signs of its potential. “F.Z.Z.T.,” in which Agent Simmons was infected with a deadly Chitauri virus, is a clear example. Tense and tightly written, the episode made it clear that both Agents of S.H.I.E.L.D. and its cast were capable of real emotional depth… and presaged the first of many heartbreaking trials to assault poor Fitz and Simmons.

1×20 – ‘Nothing Personal’

Agents of S.H.I.E.L.D. kicked into high gear after the events of Captain America: The Winter Soldier — but it didn’t peak with the Hydra reveal. “Nothing Personal” was where the heavy emotional lifting happened, as the devastated team discovered that Ward had betrayed them, and now held one of their own.

The episode was possibly Skye’s finest hour in season one, as her terror of Ward morphed into intelligent, determined resistance. And with appearances by Maria Hill, Deathlok, and the true leader of Project T.A.H.I.T.I., “Nothing Personal” became an episode we’ll remember for a long, long time.

2×10 – ‘What They Become’

Last year’s midseason finale was the fulfillment of a long promise that changed Agents of S.H.I.E.L.D. permanently. A season and a half of careful nudging led Skye to pass through Terrigen Mist, and emerge from her chrysalis as a stunningly empowered superhero. Accompanied by the devastating loss of Antoine Triplett, “What They Become” was thoroughly bittersweet — Whitehall’s death sent Cal on a rampage, while Agent 33 and Ward took their first chilling steps together.

Sure, nobody would use the word “Inhuman” in a supernatural context for several months. But the midseason finale took Agents of S.H.I.E.L.D. through it’s next drastic revolution, and opened the door to an incredible new realm of possibilities.

2×17 – ‘Melinda’

One of the possibilities raised in “What They Become” actually became relevant in “Melinda,” the episode which finally answered the question of Agent May’s mysterious trauma in Bahrain. As it turned out, a bait-and-switch with an Inhuman mother and child forced May to take a young girl’s life to save her team – a tragedy which utterly transformed her, leaving nothing of her old, hopeful life behind. With a breathtaking performance from Ming-Na, and an eerie parallel to the modern Inhuman story, “Melinda” pulled off the amazing feat of providing heartbreaking, satisfying answers to a long-percolating mystery.

3×06 – ‘4,722 Hours’

The most recent episode on our list is also Agents of S.H.I.E.L.D.‘s most unique — the episode which focused exclusively on Simmons’ six month ordeal on her lightless planet. Touching, unnerving, intense, and sad, “4,722 Hours” represents a new, risk-taking side of Agents of S.H.I.E.L.D.. Coupled with a brilliant performance from Elizabeth Henstridge, and peppered with increasingly urgent mysteries, this episode is certain to remain significant — in universe and out — for a long time.

Agents of S.H.I.E.L.D. 3×07, “Chaos Theory,” airs tonight at 9:00 p.m. on ABC.

What are your favorite episodes of ‘Agents of S.H.I.E.L.D.’?