Earlier this morning Bill Gates took to his Twitter to announce that he would be stepping in as the first-ever guest editor for TIME magazine. Gates is the first ever such editor in the publications 94-year run. Gates’s choice for cover subject illustrates his passion for saving children’s lives. Mohamad Nasir is a 5-year-old Ethiopian boy whom Gates met in 2012, and who, thanks to vaccinations against polio, measles, and more, represents worldwide milestones in early and ongoing health care.

“On the whole, the world is getting better,” Gates writes in his editor’s letter. “This is not some naively optimistic view; it’s backed by data. Look at the number of children who die before their fifth birthday. Since 1990, that figure has been cut in half. That means 122 million children have been saved in a quarter- century, and countless families have been spared the heartbreak of losing a child.”