Dinoflagellate cysts described in the literature have been linked to a particular motile stage through morphological similarities and/or co-occurrence in the same population/culture or through the technique of establishing the so-called cyst-theca relation by incubation of the cysts. Geologists use a cyst-based taxonomy, whilst biologists use a motile-stage based taxonomy. Therefore cysts can have different names than the corresponding motile stages. Living cysts can be easily isolated from the sediment using sodium polytungstate, a heavy liquid. Another method, rarely used, uses a sucrose gradient. Recent times have brought about the possibility to get molecular sequences from single cysts or single cells. The proportion of cyst-forming species for marine dinoflagellates is between 15 and 20% and for freshwater dinoflagellates 24%.