I always have problems seeing the old woman in that optical illusion who is also a young lady:
Thanks to members of the Facebook group, a group where someone will explain the joke for you if you don't get it (a great group, even though people always violate the rules by locking threads and by mocking people who don't get the joke - sometimes claiming that they thought they were in the roast group), here are illustrations showing both (for those who can't see either [or maybe even both]):
Young Lady
Old Woman
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