|In vitro fertilization|
By Medical Perspective:
In vivo means that fertilization which is occurring in human body or in the body of sexually reproducing organisms. (Natural/Normal method of reproduction)
In biological terms:
Whereas In vitro fertilization is occurred in lab, artificially, and with several humanized techniques.
For details on in-vitro fertilization read here or here.
By Chemical Perspective:
In vivo are simply those reactions occurring in the bodies of organisms, (digestion, release of endorphins, etc) while In vitro are all other reactions which are carried out in lab. (e.g Formation of acids, Formaldehyde production, Alcohol formation).
Any comment (whatever it may be) will be appreciable, as it promote thirst of knowledge.