Sarcomas are a heterogeneous class of bone and soft tissue tumors comprising over 50 different subtypes and the third most common cancer affecting children. Bone sarcomas in particular account for ~3,500 cases a year and include osteosarcoma, the most common pediatric bone tumor. Despite aggressive chemotherapy and surgical treatment, overall 5-year survivals are ~60% and less than 30% for metastatic disease. There is a dearth of sequencing data for pediatric bone sarcomas, particularly at the single-cell level. Their rarity and high heterogeneity even within the same histologic type has led to major gaps in our understanding of their molecular hallmarks, drivers and evolution. This variability is critical to understanding treatment response and failure, and there remains an urgent need to relate these molecular features to drug sensitivity and patient outcomes. We propose to close this gap by performing single-cell RNA-seq (scRNA-seq) for pediatric bone sarcoma samples. The single-cell level data will allow us to estimate the proportions of cell types in each sample and correlate these with clinical information and outcomes that will be provided for each sample as metadata.