Protocol for preparing single cells for mass-spec analysis by SCoPE2 as described by Specht et al., doi: 10.1101/665307 (2019) and Specht et al., Genome Biology, doi: 10.1186/s13059-021-02267-5 (2021). For a detailed protocol paper, see Petelski A, Emmott E, Leduc A, Huffman RG, Specht H, Perlman D, Slavov N (2021) Multiplexed single-cell proteomics using SCoPE2 Nature Protocols (in press)