Tumor tissues contain several different cell subpopulations, which complicate the detection of important genetic changes relevant to cancer development.So far, deep sequencing of tumor tissues or of cancer cell lines has provided an incomplete understanding of the genetic information and mechanisms involved in tumor progression.To provide a more comprehensive picture of the genetic changes that occur in tumors, we have carried out wholegenome sequencing at a single cell level of five common cancers: gastric cancer, liver cancer, renal cancer, bladder cancer, and leukemia cancer, and assessed the genetic changes that had occurred within these cells.We sequenced 100 single cancer cells and twenty paracancerous normal cells using the Illumina HiSeq 2000 platform, and obtained at least 2-fold coverage for each cancer type.For each cell, we recovered ~85% of the whole genome information.Our cell-to-cell comparative analysis revealed single nucleotide polymorphisms (SNPs), copy number variations (CNVs), and structural, variations (SVs) that differed between these cells.These mutations allowed us to cluster these cells into cancer and normal cell types, and then to further divide them into different subpopulations.We then carried out deep sequencing of representative single cell types and identified mutations relevant to tumor progression.These data and the use of single-cell sequencing provide novel information and useful methodology to better understand the genetic mechanisms underlying cancer development and progression .