7/23 - A new view of leeches; SETI - the search for extraterrestrial intelligence; stem cells; and a profile of Edie Widder, a specialist in marine bioluminescence.

7/30 - Phoenix Mars mission; brain trauma; mammoth mystery; Judah Folkman tribute.

8/6 - A pill that could extend the human lifespan; space elevators; satellite imaging of Mayan ruins; and a profile of "The Bacteria Whisperer."

Wednesdays, beginning 6/25/08 from 9-10 p.m. ET