<P> 1 . All living organisms are composed of one or more cells </P> <P> 2 . The cell is the most basic unit of life </P> <P> Schleiden's theory of free cell formation through crystallization was refuted in the 1850s by Robert Remak, Rudolf Virchow, and Albert Kolliker . In 1855, Rudolf Virchow added the third tenet to cell theory . In Latin, this tenet states Omnis cellula e cellula . This translated to: </P> <P> 3 . All cells arise only from pre-existing cells </P>

The idea that all living cells come from preexisting living cells was proposed by