If you are studying the gut flora of infants you would save them to run samples on a microarray, which I doubt is what our colleague will be doing with his daughter's after her debut later this afternoon. The article linked above discusses a study (http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050177) in which they used ribosomal RNA microarrays to determine the dominant gut flora of infants from birth until they turned one year old. These studies tend to look at how the gut flora is effected by the host and its environment as well as how the host is effected by their gut flora. It is possible that one day such knowledge will result in the treatment or prevention of various gastrointestinal disorders. In the mean time congratulations on your baby girl Chris!