In many biology publications, I saw that dimethyl sulfoxide (DMSO) is used to dissolve drugs. However, the cell-based assays are still performed in water-based medium such as RPMI or PBS.
My question is: If a compound is not soluble in water, what is the purpose of using DMSO? Although the drug can be dissolved in pure DMSO, won't it precipitate after putting the DMSO-dissolved compound into culture medium?