“…2). We refer the reader to other reviews that discuss the many pre-processing and quality-control steps that are required to produce 'clean', informative single-cell data (Bacher and Kendziorski, 2016;Stegle et al, 2015), and that describe methods to detect and account for uninteresting confounding effects, such as the stage of cell cycle Vallejos et al, 2015), and to analyze and account for technical noise and the so-called 'drop out' (see Glossary, Box 1) effect (Brennecke et al, 2013;Grün et al, 2014;Kharchenko et al, 2014;Pierson and Yau, 2015).…”