Changes

==Phase contrast microscopes==

==Phase contrast microscopes==

Many biological structures consist of thin, transparent, jellylike material, surrounded by water-like fluid. Even when magnified, such structures are difficult or impossible to see, because they do not affect light very much. Anyone who has ever dropped a contact lens into water should understand this. The traditional method for seeing these structures, developed in the 1900s, was to fix them (kill and harden them) with an agent like formadehyde or glutaraldehyde, and then treat them chemical dyes and stains. In the twentieth century, optical methods were developed that made these structures visible without staining. This was an important breakthrough, particularly in allowing the study of living cells.

Many biological structures consist of thin, transparent, jellylike material, surrounded by water-like fluid. Even when magnified, such structures are difficult or impossible to see, because they do not affect light very much. Anyone who has ever dropped a contact lens into water should understand this. The traditional method for seeing these structures, developed in the 1900s, was to fix them (kill and harden them) with an agent like formadehyde or glutaraldehyde, and then treat them chemical dyes and stains. In the twentieth century, optical methods were developed that made these structures visible without staining. This was an important breakthrough, particularly in allowing the study of living cells.