Petrography rock was affixed to a microscope slide and then ground so thin that light could be transmitted through mineral grains that otherwise appeared opaque. The position of adjoining grains was not disturbed, thus permitting analysis of rock texture. Thin section petrography became the standard method of rock study. Since textural details contribute greatly to knowledge of the sequence of crystallization of the various mineral constituents in a rock, petrography progressed into petrogenesis and ultimately into petrology. It was in Europe, principally in Germany, that petrography advanced in the last half of the nineteenth century. The macroscopic characters of rocks, those
(What Is) Love? she was dissatisfied with the circumstances, but was in "no way dissing Lopez." A mastered version of "What Is Love?" was included on the soundtrack to "The Back-up Plan" (2010), a film in which Lopez stars. "What Is Love?" was re-titled as "(What Is) Love?" and appeared on "Love?" (2011). "(What Is) Love?" was due to be released as a promotional single from "Love?" on April 26, 2011, but was "unlocked" and released four days earlier, on April 22, 2011 by through a campaign on Lopez's Facebook page. It was released in many European countries on April 25. The song