With the microprinter, we have the case of something old and something new. It can be two different things, depending on the context. Let's start with the old.
A microprinter is a device that prints paper copies of microfilm or microfiche "pages." The irony in this is that, as technology continues to improve and allow better and more high-quality printing of such images, the number of images that continue to be available on microfilm or microfiche is dwindling severely, especially in the wake of the digital revolution pioneered by computerized databases and Internet storage facilities. Nonetheless, microprinters exist.
Most microprinters have certain common features, with add-ons varying according to manufacturer. One common feature is a magnification lens. This lens can have a number of settings, or it can have full-on zoom capabilities. Think of a camera or microscope that has such options, and you'll understand the microprinter lenses.
Magnification is especially important if the original images presented on the microfilm or microfiche are small to begin with. This is the same sort of problem with printing images from a website or a digital camera: If the original image is small, it is usually of a low resolution, certainly lower than most standard printers. Trying to blow the image up to a viewable size on a standard size sheet of paper is usually an exercise in frustration. A microprinter's magnification lens solves this problem, however, rendering an image eminently viewable and printable at a size large enough to distinguish relevant details.
Now for the new. A microprinter is also a very small printer, designed to fit in your pocket, pocketbook, or laptop case. The microprinter is commonly in the shape of a pen or a cigar. Some microprinters can print on standard-size sheets of paper, while others are designed to print smaller. No matter the size, the paper feeds through a slot, and data transmitted from a computer or portable computing device is printed.
The original new-definition microprinters had cables just like their larger predecessors -- power cords and serial cords and such. Now, the common microprinter has just one cord, a power cord, and can even run on batteries. This microprinter connects to a laptop, PDA, mobile phone, handset, or other portable computing device via Bluetooth® or another wireless protocol.