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.
Conceived in 1884, construction of the tower began in 1887 and involved some 50 engineers, 100 iron workers, and 121 construction workers. It was completed on March 31, 1889, at a cost of 7,800,000 French gold francs. The main structure of the tower is composed of wrought-iron, coated (at present) with bronze paint. It is 324 metres (1,063 ft) in height, weighs a total of 10,000 tonnes (73 percent wrought-iron), and for 41 years it remained the tallest man-made structure in the world, until superceded by New York's Chrysler Building, designed by William van Alen (1883-1954), in 1930.