Single-cell RNA sequencing (scRNA-seq) matures into a foundational biotechnology, enabling nuanced insights into cellular heterogeneity and disease mechanisms. The International Human Cell Atlas Consortium (HCA) drives expansive cellular mapping across tissues and populations. Advances in affordable sequencing platforms, notably from Ultima Genomics, support large-scale experiments critical for AI model training and biological discovery. Researchers underscore the complexity of cells compared to proteins, increasing the need for extensive high-quality datasets. The field pivots toward spatial biology and disease inclusion, enhancing atlas utility for precision medicine.