more than 30 trillion life-forms (cells) http://www.ncbi.nlm.nih.gov/pubmed/23829164 http://www.ncbi.nlm.nih.gov/pubmed/23829164 40 trillion cells estimated http://www.ncbi.nlm.nih.gov/pubmed/23829164 http://www.ncbi.nlm.nih.gov/pubmed/23829164 37 trillion 37 trillion http://www.ncbi.nlm.nih.gov/pubmed/23829164 more than 30 trillion pieces This article A 2013 paper from Annals of Human Biology http://www.ncbi.nlm.nih.gov/pubmed/23829164 more than 30 trillion living human cells roughly 30 trillion cells http://www.ncbi.nlm.nih.gov/pubmed/23829164 PubMed 23829164 37 trillion A 2013 paper from Annals of Human Biology