John Berry, writing about Robert Slimbach’s Acumin:
Sans serifs came into their own as potential text typefaces in the 20th century, under the influence of modernist design movements. The desire to be up to the minute and to reflect a modern industrial aesthetic led to the development of many new styles of sans-serif type, including geometric and eventually humanist sans. The grotesque style itself was revived, updated, and reworked many times, most notably in the two dueling sans serifs of the late 1950s: Helvetica and Univers. These mark the point at which we can start calling a typeface neo-grotesque.