A tally of last century's scientific achievements would be a list to leave you in awe. Building on the small but important achievements of 18th and 19th century science and philosophy (with roots laid down way before), the leading minds of the era blazed a trail for future scientists to follow, and they did just that, taking us all the way through the 20th century up to the present day. From splitting the atom to manned space missions, from mapping the human genome to hitherto unimaginable life-saving leaps in medical science. Yet for all these accomplishments, there are still many important questions unanswered. These are the greatest unsolved mysteries of science.