Diatoms are generally the most important primary producers of marine and freshwaters. By absorbing CO2 in the production of organic material during photosynthesis they play a decisive role in the global carbon cycle. The complex, species-specific pattern in the structure of the cell-wall, composed chiefly of silica, can be extremely beautiful. Following death of the alga, the empty cell wall may be deposited in the sediments of lakes and oceans and be preserved as a valuable record about past environments and climate changes; as such they are important fossils for the reconstruction of millions of years of the Earth's history.
For microscopists diatoms can present a challenge: sometimes the fine structure of the cell-wall detail can only be resolved by the finest objective lenses. For comparison, diatom specialists have been able to create reference herbaria of described genera, species and varieties; one of the largest is the private collection of Friedrich Hustedt which, in 1968 was housed at the Institut für Meeresforschung in Bremerhaven (now the Alfred Wegener Institute). The collection now comprises many thousands of slides, samples and publications.