In this project, we aim to utilize public datasets (without any access restrictions) of single-cell sequencing data from pediatric cancer samples and from human embryos. The aim is to map out human embryonal tumors in the context of normal fetal development. Embryonal tumors occur due to faulty development, as they arise from remnants of developing organs. Thus, the first "hits" of tumor development occur already in fetal life. By curating several single-cell sequencing datasets from public sources, we will first build an atlas of developing cell lineages from human brain and adrenal gland. This "map" of normal development will then serve as a crucial reference for single-cell studies of human tumors. We aim to comprehensively characterize the tumor cells and compare them to normal cell states in terms of gene expression. We also aim to predict copy number variations (CNVs) and clonal heterogeneity in tumors, using corresponding normal single-cell data as reference. The aim is to identify molecular mechanisms and genetic factors related to tumor initiation, progression, and recurrence. Studies will serve as hypothesis-generating for future experimental platforms.