The tumor microenvironment (TME) plays a fundamental role in tumor progression. Cancer cells interact with their surroundings to establish a supportive niche through structural changes and paracrine signaling. Cells around transformed tumor cells contribute to cancer development, while infiltrating immune cells in this aggressive TME often become exhausted. Solid tumors, especially the most invasive types such as pancreatic ductal adenocarcinoma, are notably stiff mechanically, with cross-linking enzymes significantly affecting the survival of cancer cells in both primary tumors and metastatic sites. In this review, we highlight recent key contributions to the field, focusing on single-cell sequencing of stromal cells, which are increasingly seen as highly heterogeneous yet classifiable into distinct subtypes. These new insights enable the development of effective co-treatment approaches that could significantly enhance current and novel therapies against the most aggressive cancers.