Ectoplasm is the very thin, watery outer layer of an cell. Biologists use the word ectoplasm primarily to talk about amoebas.
Ectoplasm and endoplasm, or "dense inner section," are found in the tiny cells known as amoebas. An amoeba's movements are a result of the way these inner and outer layers fit together. A much less scientific meaning of ectoplasm is "visible spiritual energy." 19th- and early 20th-century spiritualists claimed that a gauzy ectoplasm formed during trance states, a visual connection between living and spirit worlds. This ectoplasm was often proven to be made of cheesecloth.