The word COSI stands for Center Of Science and Industry.
Although it's a great science museum, lately we have mainly been using our membership to take advantage of the fantastic indoor playspace on the second floor - it has great play structures, and pretend houses, doctor's office, ambulance, helicopter, grocery store, you name it. There is even a little water play area where the kids can don raincoats and splash in the water table and play with squirt guns.In the Ocean exhibit, preschoolers can balance balls on streams of water, make imprints in the sand, and even create their own water flow by manipulating plumbing parts.
Older kids can check out the inner workings of everyday household appliances in the Gadgets exhibit, or try cool hands-on experiments including acids and bases, circuits, brain teasers, and even seltzer explosions.
COSI also has an IMAX theater, and tons of family programs and camps.
The only downside to membership is that it doesn't cover parking - what's up with that? Otherwise, two thumbs way up.