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 The term “nannofossils” refers to a group of organisms of a size which require the use of a high-powered microscope capable of magnifying around 1000-1500x. Most fossil specimens are around 2-20 microns in size. They are normally examined in thin section preparation by transmitted light with polarisers and a “slow wave” plate.
+Although other "rock-forming" fossils are known, nannofossils are by far the smallest, yet are responsible for several thousand metres of chalk thickness across much of the planet in Cretaceous times.
 The processing of nannofossils for examination normally involves the sediment being mixed with water and spread or ‘smeared’ onto the surface of a microscope slide, dried and then covered with a coverslip attached with an optical adhesive.  There is a standard preparation method, but most nannopaleontologists have their own adaptations for coping with the variety of lithologies that they encounter at wellsite.
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 The term “nannofossils” encompasses a wide range of plant derived fossils which have (a) a common size and (b) significant geological utility. These may include coccoliths, nannoconids, pentalithssphenoliths, discoasters and even calcareous dinoflagellate cysts. However, coccoliths, nannoconids and discoasters are the predominant types found in this particular group. Their characteristics are: