Plants possess unique properties that distinguish them from all other living things. The “green” plants comprise a very diverse group of organisms from algae to bryophytes, gymnosperms, and angiosperms that are considered true plants. On a cellular level, the vast majority of plants contain the pigment chlorophyll and are the primary producers on planet Earth, on land, and in water. These organisms have life cycles that encompass an alternation of generations from a haploid generation to one that is diploid. The complexity associated with these groups can be attributed to the evolution of land plants from ancestral ties to the blue-green algae (cyanobacteria) and algae (eukaryotes).