Emma Wedgwood, Charles Darwin's wife and cousin, wrote about the ordinary life the couple enjoyed despite the controversy surrounding her husband's ideas on evolution.
The collection includes 60 diaries that stretch to 6,000 pages in total, covering the years 1824, 1833-4, 1839-45 and 1848-96.
They include Emma's life as a 16 year-old girl and the run-up to her death at the age of 88 in 1896.
Charles's health is commented on frequently as he battled a mystery disease that gave him blackouts and made him retch.
Emma also uses a number of codes within the diaries, including marking her menstruation periods with a large X.
However, the perfunctory writing style is summed up by Emma's note on the date of Charles's death, with the entry simply reading 'Fatal attack at 12'.
Dr John van Wyhe, the project's director at Cambridge University, said that the diaries were the latest part of an expanding online collection based on Darwin's work.
"As vast as the collection now is, there is much still to come before 2009, the bicentenary of Darwin's birth and the 150th anniversary of the publication of the Origin of Species," he said.
Forthcoming materials include further editions and translations, and images of the majority of the Darwin Archive at Cambridge University Library.
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