There are a couple, at least, on the ISS.
The main one seems to be the Light Microscopy Module.
Light Microscopy Module (LMM) is housed within and used in
conjunction with the glovebox in the Fluids Integrated Rack (FIR).
Images provided by the LMM can provide data to scientists and
engineers to help understand the forces that control the organization
and dynamics of matter at microscopic scales.
The LMM microscope is
capable of using most standard Leica objectives. The present on-orbit
compliment includes: 2.5x,10x, 20x, 40x, 50x, 63x, 63x oil, and 100x
oil, objectives. New or different objectives may also be flown as
The LMM contains a digital black and white low noise
scientific camera. PI specific specialty cells (sample holders) are
under development for temperature control and electric field
experiments. Three dimensional (3D) confocal (point illumination)
upgrades are scheduled for 2015-2016.
The Light Microscope Module
(LMM) flight unit features a modified commercial off-the-shelf (COTS)
Leica RXA microscope, which is configured to operate in an automated
mode with some interaction from the ground support staff or the
astronaut crew. The microscope is modified and enhanced to provide
additional capabilities including, video microscopy to record sample
features including basic structures and crystal growth dynamics and
basic biological system observations. Currently, demonstrated
imaging techniques use a high resolution black and white microscopy,
bright field, epifluorescencent (EPI), and fluorescent techniques.
investigator can choose from standard Leica objective lenses of
different magnifications. This suite of measurements enabled by the
LMM allow for a detailed characterization of fluids, colloids, and
two-phase media, including biological samples. A backlighting LED
sample holder was also developed to enhance biological imaging, and is
available onboard the ISS.
The LMM was recently (May 2017) upgraded with "a laser light package, scanner and two high-resolution digital scientific cameras. In addition to 3D imaging, this update will significantly improve the microscope’s resolution and contrast by eliminating unnecessary light." (source)
New to me was the NanoRacks Microscope.
Send us your slides and have ISS crew members take pictures during
your 30 day mission.
I hope that's not as "name a star after yourself" as it sounds.
Curiosity has a "Hand Lens", the Mars Hand Lens Imager.
The self-focusing, roughly 1.5-inch-wide (4-centimeter-wide) camera
takes color images of features as small as 12.5 micrometers, smaller
than the diameter of a human hair.
To me this conjures up images of a robotic Sherlock Holmes peeking through his magnifying glass, so perhaps this is not considered a microscope.