William Hallowes Miller
(Born 6 April 1801): Welsh mineralogist who developed a system for describing crystal structures using a set of three integers to designate each crystal faces. The publication of his work in A Treatise on Crystallography in 1839 addressed the confusion arising from the many different descriptive systems previously used (see The Papers of John Hallowes Miller – Archives Hub (jisc.ac.uk), William Hallowes Miller – Wikipedia and April 6 – Today in Science History – Scientists born on April 6th, died, and events).
(Born 14 April 1927): New Zealand-American chemist, who received the Nobel Prize in Chemistry in 2000 for his contributions to the development of conducting polymers (see Alan G. MacDiarmid Biographical – NobelPrize.org and April 14 – Today in Science History – Scientists born on April 14th, died, and events).
(Born 19 April 1946): Spanish inorganic and sol-gel chemist, whose achievements were celebrated in the March 2021 issue of the ISGS Newsletter (see People in the Spotlight – Professor María ValletRegí (isgs.org) and María Vallet-Regí, Date of Birth, Place of Birth (bornglorious.com)).
more of the Sol-Gel (and Materials Chemistry) History you can find here