This undifferentiated embryonic structure then undergoes a phase of major cell migration called gastrulation, producing a gastrula with three separate germ layers: the endoderm, mesoderm, and ectoderm. Endoderm The endoderm is formed from cells that migrate toward the center of the developing gastrula.
The Eiffel tower is made of puddled iron. It is made up of steel in steel X's. The Eiffel Tower is made of iron. The Eiffel Tower is made of pure iron.
The construction of the Eiffel tower. Eiffel Tower. Work began in January 26th, 1887 with the digging of the Tower's foundations, which were laid in four months. The work started on July 1st, 1887 to end twenty-one months later. All the elements were prepared in Eiffelâs factory in Levallois-Perret, on the outskirts of Paris. Each of the 18,000 pieces used to construct the Tower was specifically designed and calculated, traced out to an accuracy of a tenth of a millimetre and then put together to form new pieces, each measuring around five metres.