Mathematicians discover a new type of pentagon that can cover the plane leaving no gaps and with no overlaps. It becomes only the 15th type of pentagon known that can do this, and the first discovered in 30 years.
Previously on Mefi: No Pentagons (main link isn’t working, but check out The Trouble with Five and this article on Marjorie Rice, an amateur mathematician who discovered four of the 15 known pentagonal tilings, linked in the comments.)
Bonus for ’80s math-nerd kids: “Tessellations” song from Square One Television. Ooh-bop-bop-ooh!