• A typical stereoptic microscopemicroscope image by guy from Fotolia.com
  
  The first optical microscopes were invented in the 16th century by Dutch spectacle makers Zachariah and Hans Jensson, and greatly improved by Anthony Leeuwenhoek. Microscopy has been part of science ever since. Attempts to use microscopy to identify three-dimensional structures in samples started in the 19th century, with significant enhancements in the field appearing in the first half of the 20th century.
  
  

Stereoptic Microscopy

• Stereoptic microscopy uses two focusing arrays aimed at the same slide sample from slightly different angles to generate a 3-D perspective on the slide. This common technique in laboratory work has been in wide use in medical research since the 1920s.
  
  

Confocal Microscopy

• Confocal microscopy uses a scanning point of light to generate reflections (and refraction patterns) from a slide sample. Excellent resolution make it a great tool for minimizing the impact of "out of field" light that can wash out the slide. Because the angle at which the scanning point of light can be precisely controlled, confocal microscopy can be used to "change the lighting" of cellular structures on the slide, much the same way that time-lapse photography can enhance the 3-D perception of landscapes by allowing shadows to shift. Confocal microscopes have been used since the early 1960s.
  
  

Scanning Electron Microscope

• A scanning electron microscope is similar in concept to a confocal microscope, save that the beam of photons is replaced with a beam of electrons. A 3-D image is assembled from the range of particles (electrons, photons and back-scattered electrons) released by the target when the electrons interact with them. It generates significant depth of field in its images. Most commonly published scanning electron microscope images rely on secondary electron emissions. Different detectors can be built into an SEM, but it's unusual for a scanning electron microscope to have all of them.