It is said that around 90% of the cells in a human body are symbiotic bacteria living thanks to us. When we die, do most of them also die? Or do they manage to survive without us and find a new 'home human'? And opposite, when and how do we get all those bacteria after conception? Do we get some already from the mother while embryos in the womb? If so when do they start to 'invade' our body? Or do we get them only after birth and by which mechanisms?