Colorectal Cancer Cohort

* Stool collection prior to starting treatment (i.e. chemotherapy, chemoradiotherapy, etc.)~* Blood sample to be collected either prior to starting treatment (i.e. chemotherapy, chemoradiotherapy, etc.) or during surveillance.~* Prospective tissue collection will be utilized from clinically indicated diagnostic colonoscopies/biopsies/resections s, including surveillance colonoscopies. Non-diagnostically indicated tissue collections will not be performed. Some EOCRC patients will have already undergone prior surgical resection, with tissue (including normal colonic mucosae distant from the malignant tumor). The pathology FFPE blocks may be used as a source of normal colon tissue for genomic analysis.

Healthy Control Cohort

Tissue collection of normal colon mucosa will be utilized from clinically indicated colonoscopies or from tissue obtained from a prior colonoscopy, non-diagnostically indicated tissue collections will not be performed. Colonoscopies for indications of IBD, anemia, and/or genetic predisposition will be excluded.~* Stool samples will be collected at time of colonoscopy. Samples to be collected either within 3-14 days before or at least 14 days after colonoscopy, to avoid changes in microbiome caused by colonoscopy prep.~* Blood samples will be collected at time of colonoscopy.~* Risk factor questionnaire will be completed at time of colonoscopy. Will also try to collect stool from healthy control patients; however, if accrual is low after 3-6 months, remainder of cohort will be filled with specimen data from the Human Microbiome Project Data Portal.