Dr. A.P.J. Abdul Kalam was one of India's most distinguished scientists before becoming President from 2002-2007. He was a renowned aerospace engineer who played a key role in India's missile development program and nuclear capabilities, earning him the nickname 'Missile Man of India'. Dr. Zakir Hussain was an educationist. R. Venkataraman and Neelam Sanjiva Reddy were politicians rather than scientists.