If you look at the following diagram you can see 4 major developmental processes that occur in human embryogenesis.

• Cell Division (Cleavage)--Converts 1 cell to many; the egg is one cell, the embryo is multicellular; the conversion from one cell to many involves an initial cleavage (embryonic mitoses) phase followed by regular mitotic cell divisions. 
  
  
• Cell Differentiation--formation of different, specialized cell types; the egg is one cell type, the embryo contains hundreds of cell types; understanding how cells specialize is a fundamental problem of developmental biology 
  
  
• Morphogenetic Events--literally the "generation of shape", morphogenesis results in the embryonic organization, the pattern & polarity to cells, organs & tissues; the egg is round while the embryo is has a specific organization of multiple layers of different cells; the terms morphogenesis and differentiation are not synonymous although many researchers today make this mistake in terminology; cell differentiation is just one component of morphogenesis.
  
  
• Growth--Increases size of organism; the embryo increases dramatically in sized from the next to invisible egg to the full grown fetus.  

This information was provided by Professor Danton H. O'Day - Univerisity of Toronto at Mississauga - Canada. Unless otherwise stated the information and graphics that are presented within this embryology section are the sole property of Danton H. O'Day, copyright 1998(c), 1999(c), 2000(c), 2001(c), 2002(c).

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