Cecilia Payne-Gaposchkin (May 10, 1900 – December 7, 1979) was an English-American astronomer who in 1925 was first to show that the Sun is mainly composed of hydrogen, contradicting accepted wisdom at the time.
Suggestion for those with multiple children:I use colored index cards and designate a color for each kid. On the cards I listed everything they need to master. As that child masters things, I check it off on their card, which is kept in the front of the box. Cards don't leave the review section until everyone's got it. So, as I start a lesson, I take 2 seconds to flip through the review cards and take out what that kid needs.