library_construction_protocol: Single cells from the mammary gland organoid from Matrigel (MATR), soft (SOFT), collagen (COL1) and stiff (STIFF) condition were dissociated. Dissociated cells were labelled with TotalSeq-A hashtag oligonucleotide (HTO) antibodies. Matrigel and soft, collagen and stiff were pooled and loaded onto each channel of the Chromium Single Cell 3′ microfluidic chips (V2- chemistry, PN-120232, 10X Genomics) and barcoded with a 10X Chromium controller according to the manufacturer's recommendations (10X Genomics). RNA from the barcoded cells was subsequently reverse transcribed, followed by amplification, shearing 5′ adaptor and sample index attachment. The libraries were prepared using the Chromium Single Cell 3′ Library Kit (V3-chemistry, PN-120233, 10X Genomics) and sequenced on an Illumina Novaseq 6000 (paired-end 100bp reads).