The Going Out Guide recommends free things to do for every day of the week.
It's the last day to view photographer David Liittschwager's works that explore the variety of life within a single ecosystem. Liittschwager placed a 12-inch cube in different environments and photographed the creatures who wandered into it.
10 a.m. to 6 p.m. National Geographic Museum, 1145 17th St. NW. 202-857-7588. www.nationalgeographic.com.
Georgetown University's Center for Contemporary Arab Studies screens the controversial 2010 film "Two Girls from Egypt." Set in contemporary Cairo, it tells the story of two well-educated, single women in their thirties struggling with society's ideas about "spinsterhood."
5 to 7 p.m. Georgetown University, Center for Contemporary Arab Studies, 3700 O St. NW. 202-687-5793. ccas.georgetown.edu.
Three teen performers present their responses to the question "Whose world is this?" from Nas' 1994 track "The World Is Yours." Hosted by the Creative Ecosystem's Youth Leadership Committee, DC Youth Slam Team and Freshh Inc., the event is part of the Kennedy Center's "One Mic: Hip-Hop Culture Worldwide" festival.
6 p.m. Kennedy Center, 2700 F St. NW. 202-467-4600. www.kennedy-center.org.
Meet up at the Thomas Jefferson Memorial to learn facts about the District's cherry blossoms from a National Park Service ranger. Gifts from Japan, the trees were planted in the National Mall and memorial parks in 1912. The ranger-led cherry blossom tours take place daily until the National Cherry Blossom Festival ends on April 13.
At 10 a.m., noon and 2, 4 and 6 p.m. daily. Thomas Jefferson Memorial, 900 Ohio Dr. SW. www.nationalcherryblossomfestival.org.
Co-sponsored by NASA, Defense Advanced Research Projects (DARPA) and Infamous Robotics LLC, this event has product demonstrations from Infamous Robotics LLC's Robotics Inventors Club, DARPA and several university robotics teams, including groups from George Washington University, Cornell University and the University of Maryland.
11 a.m. to 4 p.m. National Air and Space Museum, 600 Independence Ave. SW. 202-633-2214. airandspace.si.edu.
Duke it out with friends and total strangers in honor of International Pillow Fight Day. (It's a thing. Seriously.) The host, Capital Improv, stresses the importance of keeping the "prank" element of the fight alive by hiding all pillows until the fight begins. And the fight's not without rules: kids are advised to fight outside of the main group, down pillows are forbidden and guests should swing lightly and refrain from hitting people with cameras or without pillows.
2 to 4 p.m. Washington Monument grounds, 15th Street and Constitution Avenue NW. 2014.pillowfightday.com.
Celebrate the Bard's 450th birthday at this family festival featuring live music and theater performances, jugglers, crafts, jesters, swordplay, a tour of the Folger's reading rooms and, of course, birthday cake.
Noon to 4 p.m. Folger Shakespeare Library, 201 E. Capitol St. SE. 202-544-4600. www.folger.edu.