Averaged measurements could present the common pattern shared among the sample but not the individual information contained in different cells, which is so-called cellular heterogeneity. The decompositions of heterogeneity may uncover much functionally-important information, as stated below.

MS-based SCP will drastically advance our understanding of human health and disease, especially with the combination of single-cell transcriptomics and genomics (single-cell multiomics). [6,7] However, it still has some technical challenges, including preparation of the tiny amount of proteins in single cells for MS measurements and ultrasensitive detection and identification of proteins using MS. [5] Recently, our lab developed a novel Nano3 technique for preparation of a small number of human cells (i.e., 10 HeLa cells), enabling the identification of over 1000 proteins and dozens of transcription factors from only 10 HeLa cells. (Figure 2) [8]