How many are there? about 150 genera with about 2000 species.
	How old are they? 2.8 to 2.5 billion years old with stromatolites as living fossils.
	Where are cyanobacteria found? Many species in freshwater habitats including thermal springs and soil. Many species in marine habitats as well. In Hawai'i, Lynbya majuscula is probably our most common marine species.

	How are their cells organized? Bacterial organization.
	What pigments do they possess? Chlorophyll a and phycobilins assembled as a phycobilisome on thylakoid membranes.

	How is the chloroplast constructed? Thylakoids do not stack at all; they form NO grana. There are no chloroplasts.
	What storage product is made?  Cyanophycin starch {with alpha 1,4 linked glucans}.
	Cell wall features? These are gram negative bacteria with a 4 layered cell wall; murein (peptidoglycan)  as rigid structure. Many also possess polysaccharide matrix that envelopes cells (Anacystis) or sheath that cover cells in filaments (Lyngbya).
	Cells diversity and complexity is surprising for "bacteria".  A few species remain as unicells but show no sexual reproduction. Aggregations of cells into "trichomes" occurs  (Lyngbya). Filaments occur when trichomes are surrounded by a sheath. Cell differentiation results in "spores", akinetes and heterocysts. Take a look at this sampling of Cyanophytes.

Simple to increasingly complex (Order Chroococales).

	Anacystis
	Coccochloris
	Agmenellum

All of these genera reproduce asexually.

Increasing complexity but single cell that produces "spores" (Order Chamaeosiphonales).

Entophysalis

Increasingly complex  morphologies (Order Nostocales) with   cell differentiation into heterocysts and false branching in some genera.

	Anabaena
	Calothrix
	Cylindrospermum
	Rivularia

Tolypothrix

All of these genera reproduce asexually

Most complex morphology result in the most advanced order, the Order Stigonematales. This group of  bluegreens exhibits multicellular growth via true branching.  Heterocysts still occur.

	Stigonema
	Hapalosiphon

All of these genera reproduce asexually.