The Paganini Variations were composed in 1863 and were Brahms homage to the great Paganini. It was meant as a work of study for playing the piano, but one must be particularly ambitious to master this pianistic hell. Its technical demands are extreme, maybe meant to mimic the Italian violin master.
Paganini’s 24 Caprices, and especially the last one, was an inspiration for a whole host of composers during the classical era, but also much later (Liszt, Rachmaninov, Lutosławski and Chopin to name a few). It also made it into the realm of pop music, and I might make some people happy by mentioning prog rocker Yngwie Malmsteen who used it on his song Prophet of doom.