Cheng Ho was born around 1371 in China's southwestern Yunan Province (just north of Laos) with the name Ma Ho. Ma Ho's father was a Muslim hajji (who had made a pilgrimage to Mecca) and the family name of Ma was used by Muslims in representation of the word Mohammed.
When Ma Ho was ten years old (around 1381), he was captured along with other children when the Chinese army invaded Yunan to take control over the region. At the age of 13 he was castrated, as were other young prisoners, and he was placed as a servant in the household of the Chinese Emperor's fourth son (out of twenty-six total sons), Prince Zhu Di. Later his name was changed to Cheng Ho by the prince.
Cheng Ho, who was said to have been seven feet tall, was given greater power when Zhu Di (or Chu Ti) became emperor in 1402. The new emperor took the name Young Lo . One year later, Young Lo appointed Cheng Ho admiral and ordered him to oversee the construction of a Treasure Fleet to explore the seas surrounding China. The first three voyages explored Asia. The fourth till the seventh also go to East Africa.
When emperor Young Lo died in 1424 and his son Zhu Gaozhi became emperor. He canceled the voyages of the Treasure Fleets. Cheng Ho was appointed military commander of Nanjing. Zheng He flag "treasure ship" is four hundred feet long - much larger than Columbus's. In the drawing, the two flagships are superimposed to give a clear idea of the relative size of these two ships.
Admiral Zheng Ho was not the first to travel from China to Africa.

The Quanzhou wreck from 150 years earlier.

The best archeological evidence available comes from the wreck buried in muck at Houzhou. Houzhou lies about six miles from Quanzhou, an important Song trading port in what is now Fujian Province. The ship was about 114 feet long by 32 feet wide, with a displacement of roughly 375 tons. The archeologists found more than 500 copper coins associated with the wreck, 70 of which were minted during the Southern Song period (ca. 1127-1279), with the latest ones dating to 1272. The ship probably sank soon after that date. Associated with the ship remains were about 5,000 pounds of fragrant wood, probably from either mainland or island Southeast Asia, and assorted materials such as cowry shells, ambergris, cinnabar, betel nut, pepper, and tortoiseshell, the ambergris attributed to Somalia (after tests). These archeological associations could just as easily have resulted from tramping -- that is, ships not making point-to-point voyages but taking on and trading cargo at various ports along the way --