Each volunteer must be: (i) male or female, 50 to 75 years old, undergoing routine colonoscopy, (ii) without any history of CRC or IBD, (iii) without having antibiotics or suffering from gastroenteritis for the past month, (iv) without requiring blood thinning medication 2 days before and 2 days after the colonoscopy. The histopatholostists will assess if any tumors found are malignant or merely hyperplastic polyps and their size. Accordingly volunteers without tumors will be categorized as (a) healthy-appearing, while the rest as either (b) CRC-prone, or (c) CRC-bearing. CRC-prone will be considered those bearing ≥3 adenomas/serrated polyps, or ≥1 adenoma/serrated polyp ≥1cm, or ≥1 villus adenoma, or High Grade Dysplasia (per Lieberman et al Gastroenterology 2012). Based on tumor histopathological analysis 32 individuals considered at risk for CRC will be selected as “CRC-prone”. 64 without any tumors will be used as the control group. “CRC-bearing” individuals will be excluded due to potential secondary effects on the colonic mucosa.