Summary: This CloneSeq protocol combines clonal expansion inside 3D hydrogel spheres and droplet-based RNA sequencing to resolve the limited sensitivity of single-cell approaches. CloneSeq can reveal rare subpopulations and support cellular stemness. CloneSeq can be adapted to different biological systems to discover rare subpopulations by leveraging clonal enhanced sensitivity. Important considerations include the hydrogel composition, adaptation of 3D cultured clones to the inDrops system, and inherent adhesive properties of the cells. CloneSeq is only validated for cell lines so far.For complete details on the use and execution of this protocol, please refer to (Bavli et al., 2021).