CCs are the most primitive meteorites found.
That is, they have experienced the least alteration since the time they formed and so are the best physical record of the events that transpired to form our solar system. These minerals are significant because they formed by reaction of anhydrous minerals with water. If formation took place on the meteorite parent body, perhaps liquid water was present within asteroids, which suggests these bodies once had active hydrothermal systems much like earth. By studying the mineralogy within the CMs and comparing this mineralogy to terrestrial analogs, it is possible to better understand the way these minerals formed. TEM allows one to study the structure and chemistry of a material at the atomic scale.