One of the key discoveries in the field has been that microRNA function is highly dependent on context. For example the transcriptional program of a given cell can greatly influence which transcripts are available for a given microRNA to target. To get towards a comprehensive understanding of microRNA function, we propose single cell studies.However, the changes induced by miR-146a expression may be heterogeneous across a population, and this heterogeneity can cause effects at the single cell level to specify cell fate decisions. Even when a tissue contains cells of the same type, the expression of a particular protein can show stochastic cell-to-cell variation as well as intracellular temporal fluctuations. Sometimes these fluctuations can be dramatic- up to ~1000 fold between the low expressing and high expressing cells at a given point in time. Recent reports suggest that such non genetic heterogeneity might be generated by miRNA-mediated effects on gene expression, and that this depends on the number of miRNA binding sites in the 3'UTR, the level of target mRNA in the cell, and the level of miRNA in the cell. The net effect of these is to cause a threshold effect- and that our conventional thinking about miRNA- partial repression of gene expression- may only hold for intermediate concentrations of the miRNA. In experiments with miRNA over expression or knock down, most group0s usually collect the RNA from an entire population of cells, revealing a snapshot of the average gene expression in the cells. This certainly doesn't tell us the entire story-different cells with differing unperturbed target mRNA levels would have different levels of change, depending on the mRNA threshold. Therefore, single cell expression studies are necessary to study cell-to-cell variation in response to miRNA's.