The last couple of years I've become really fixated on/fascinated by the evolution of the Starfleet uniform across the years. Sometimes it's such an obvious next step, other times it's a bizarre departure, but I always find it interesting. Let's do pictures!
#StarTrek 1/x

So, PRE-Trek and in the real world, we've got the NASA astronaut jumpsuit. These two photos are of mission crews from 2000 & 2019 - not a huge amount of variation in the design.
#StarTrek 2/x

Starting in the 2140s, the first Starfleet uniform design clearly takes its inspiration from NASA, with a few quirks of its own: coloured department shoulders and rank pips on the shirt. By the early 2160s, just minor changes - epaulets, a nametag, and an arm patch.
#StarTrek 3/x

That brings us to just after the Earth-Romulan War and the founding of the Federation. Here in the mid-2160s the design still draws on NASA, but is a much more marked departure. It does preserve the prior design's colours though - gold for command, blue for science.
#StarTrek 4/x

70 years later, there's a MASSIVE change in design. Here blue apparently means command, and there's a stripe around the shoulders that's reminiscent of the ENT and later TNG shoulders, and the Starfleet symbol is now a physical badge, not a patch.
#StarTrek 5/x

Just 6 years later, a new design is in use which is a more natural evolution of the ENT uniform, restoring primarily navy colouring, straight lines, & 90° angles. Rank is depicted on the Starfleet badge itself. This one was in process of being phased out by 2257.
#StarTrek 6/x

Concurrently with the latter days of that uniform, Starfleet seems to have been testing a return to brightly-coloured shirts, first as a kind of sweater, and then incorporating design elements from the DSC-type uniform.
#StarTrek 7/x

The 2260s are a bit of a ride. In 2265, they were back to using sweater uniform tops, and then the next year adopted the classic TOS uniform design, which remained in use till at least 2269. Rank is on the sleeves & the Starfleet symbol is again sewn into the shirt.
#StarTrek 8/x

(Or maybe Where No Man Has Gone Before just happened to land on the Enterprise's laundry day)

Perhaps the less said about 2273, the better.
#StarTrek 9/x

In approx 2278, one of the most enduring & iconic redesigns came into use. The Starfleet symbol is a redesigned badge, coloured undershirts depict department, and rank is shown as a design on the shoulder. This uniform would be unchanged till at least 2293.
#StarTrek 10/x

Things change though, of course. By the 2320s, the more formal collared undershirt became simply a coloured undershirt poking out from beneath the red.
#StarTrek 11/x

More changes followed in the 2340s: by 2344 the undershirt was gone entirely, along with the belt, and by 2348 the Starfleet badge has changed into the one we're more familiar with from TNG.
#StarTrek 12/x

By 2364 Starfleet returns to bold, TOS-esque bright colours dominating a onesie (and reversing red/command and gold/ops), and rank pips added to a collar. This was modified into a 2-piece with no shoulder stripe the following year, and remained in use till 2369.
#StarTrek 13/x

In 2370 Starfleet makes the slightly puzzling choice to adopt a variant on its cadet uniform design as the standard officer's duty uniform, albeit with a more casual 'neckline' and greyish undershirt. The Starfleet badge also undergoes a minor redesign.
#StarTrek 14/x

Just 3 years later in 2373, Starfleet turns to a more formal design, preserving the black body but implementing standard grey shoulders and a division-coloured undershirt, a callback to the 2280s uniform. This uniform remains in use till the end of the decade.
#StarTrek 15/x

2380 sees a reset of sorts, with uniform design pivoting back to a bold colours more in tune with uniform of the 2360s, albeit with some more formal lines worked into the top. The Starfleet badge has also received another minor redesign.
#StarTrek 16/x

Within five years, by 2385, Starfleet has again pivoted, this time back to a look similar to that of the early 2370s with a black body and division-coloured shoulders. The 2385 design has a bit more flair than the 2370s look, and the 2369-79 comm badge returns.
#StarTrek 17/x

By 2399 the design has very naturally evolved; we're back to fully coloured division shoulders, which now have texturing to them. The command pips are back on the shirt a la the 2150s uniforms, and the Starfleet badge has been significantly redesigned.
#StarTrek 18/x

As an aside: the 2399 Starfleet comm badge is a riff on a similar design we saw in three different alternate futures, depicted in All Good Things..., The Visitor, and Endgame.
#StarTrek 19/x

Skipping ahead over 400 years to the 29th century, the Starfleet uniform and comm badge designs have changed dramatically, but you can still see echoes of 22nd-24th century designs: distinct shoulders, comm badge on the left breast, rank pips on the collar.
#StarTrek 20/x

Another 200 years after that, in the 31st century, it's not even clear whether Starfleet still exists in any form we would recognize. Our only point of reference is temporal agent Daniels, whose uniform(?) is utterly removed from anything seen before.
#StarTrek 21/x

What will Starfleet officers look like when Discovery arrives 100 years later, in the 32nd century? Does a recognizable Starfleet even still exist?

Your guess is as good as mine, but I'm excited to find out! October 15th, gang!
#StarTrek 22/22

Brief thread revival: late 32nd century standard uniforms! I'm not totally clear on the difference between Lt Willa & the captains, but you can see certain things inherited - pleated texturing, evolved rank pips design but which mean the same, epaulets similar to the TMP uniforms