Today I learned that Mr. Wizard passed away on June 12, 2007 after a battle with bone cancer. Mr. Wizard — you made a science geek out of me.

From his website:

It is with deep sadness that we regret to announce the passing of Don Herbert - the one and only “Mr. Wizard”. Don lost his battle with cancer today, June 12, 2007, at 9 AM Pacific Daylight Time - slightly more than one month shy of his 90th birthday. He was lovingly surrounded by his family, who are at once, saddened by his passing, and relieved that he is no longer suffering.