In 1980, Kenner expanded its Star Wars toy line to include the metal miniature figures and playsets that make up the Micro Collection. This line of toys had three themes to it; Death Star, Hoth, Bespin. All together, there were nine sets released to toy stores, and two mail away packs.
The Death Star theme consisted of two playsets; the Death Star Escape and the Death Star Compactor. Each was a plastic playset that included painted metal figures. The Compactor came with eight while the Escape only came with six.
The Hoth theme was the largest of the three. It consisted of three small sets, and one large set. The Generator Attack set was a white plastic base with a grey plastic generator that exploded and an AT-ST, and six figures. The Wampa Cave set came with a white plastic cave, a mostly plastic, exploding Probot, and four figures. The Turret Defense was again a white plastic base that came with two exploding turrets and six figures. Finally, the Ion Cannon playset was the largest of the four. It consisted of a movable Ion Cannon, shield doors that opened and closed by a moving a look-out tower and came with a couple computer banks. The set also came with eight figures. These four sets could be connected in any order through puzzle piece like extensions on the bases.
The Bespin theme consisted of three sets. The Gantry is a grey plastic base that looks like where Luke jumps off to avoid Vader, it came with four figures, two Lukes and two Vaders. The Control Room simulated the window through which Luke get pulled in his fight with Vader, it had "breaking" windows, and four figures. Finally, the Freeze Chamber was the large area in which they froze poor old Han. This one came with eigth figures. The two smaller sets could be attached to the Freeze Chamber at certain spots.
Through various offers, one could order a couple of sets of figures. The "build you armies" set was six figures. Three were Hoth rebels, and three were Snowtroopers. The other one I know of, which isn't listed in most places, was offered through the C-3PO's cereal. It came with Luke Skywalker, Princess Leia, R2-D2 and C-3PO.
There are also several unreleased, and prototype MicroCollection items that people know of, and collectors go crazy over. The line was discontinued due to unpopularity. At that time, there wasn't much of a market for non-poseable figures. So plans Kenner had for more sets were scrapped. These unproduced sets include a Bacta Chamber, an Interrogation Room, Dagobah, and the Emperor's Throne Room.
A little known fact about the MicroCollection figures and sets is that they were given a numbering systems which indicates which figures go with which sets. On all of the figures, except the Probot, there is a six digit number, xxx-xxx. The first three digits indicate which set the figure belongs to and the last three are the figure's own ID number. Thanks to Ron Salvatore for this info. You can download the list with the sets, the figures and the numbers here.
For more information about the MicroCollection line see the Star Wars Toy Resource Page. And for information about the unreleased MicroCollection figures see The Star Wars Collectors Archive.