stepping stone

1. Lit .: A raised stone in a stream or swampy places, by stepping on which a person may cro without wetting or dirtying the foet. 2. Fig .: An aid or means for the accomplishment of an end or the gaining of an object; a help, an ad vantage. "Those obstacles his genius had turned into stepping stones."- Macaulay : Hist . Eng . , ch. xi.