Organogenesis occurs within the first trimester of fetal development.

Organogenesis is the process by which a mass of cells in a developing embryo differentiates and develops into a functioning organ. In the embryo, all cells are basically stem cells and all alike. Once the process of organogenesis takes place and the beginnings of specialized organs form, the fetal stage begins.

The nervous system

organogenesis:

-production of UNIPOLAR structure (shoot OR root PRIMODIUM)

-vascular system CONNECTED to parent tissue

somatic embryogenesis:

- production of BIPOLAR structure (shoot AND root axes)

- vascular system NOT CONNECTED to parent tissue

Gametogenesis

Fertilization

Cleavage

Gastrulation

Organogenesis

and the Later Stages (Growth)