FIGURE 1.

Principles and workflow of recently developed spatial transcriptomic techniques. Two spatial transcriptomic strategies with recent development can be broadly categorized as FISH-based and sequencing-based. FISH-based methods improve on its signal detection (branched MERFISH), diffraction limit (osmFISH and seqFISH+) and gene coverage (seqFISH+). In situ sequencing has been combined with tissue clearing technology and modified sequencing by ligation to improve deep tissue visibility and sequencing error in STARmap. Aside from that, many recent techniques are in favor of in situ indexing, either by utilizing immobilized (Visium Spatial, HDST, Slide-seq) or flowing (DBiT-seq) barcoded oligonucleotide, followed by in vitro sequencing.