No wonder 'Childhood & Memes' has such a huge following. Krystine Batcho, Ph.D., is a licensed psychologist and professor at LeMoyne College and she believes that nostalgia is an emotional experience that unifies.

"One example of this is it helps to unite our sense of who we are, our self, our identity over time," Batcho explained.

"Because over time we change constantly, we change in incredible ways. We're not anywhere near the same as we were when we were three years old, for example. Nostalgia, by motivating us to remember the past in our own life, helps to unite us to that authentic self and remind us of who we have been and then compare that to who we feel we are today."

That gives us a sense of who we want to be down the road in the future as well.

"The other way that nostalgia serves an essential psychological function is that it is a highly social emotion," Batcho added. "It connects us to other people"

Nostalgia does that in many beautiful ways, not just memes. "In the beginning, when we're very young, it's part of what bonds us to the most important people in our life, our parents, our siblings, our friends. As we go through life, it can broaden out and extend to a wider sphere of the people we interact with"

"It's a social connectedness phenomenon and nostalgia is in that sense a very healthy pro-social emotion," the psychologist added.

Nostalgia also helps us to unify what otherwise would be felt or experienced by us as conflicts.

"In itself, it is somewhat of a conflict because as I define it is a bitter-sweet emotion," Batcho noted. "It's sweet because we're remembering the best times, the good times of our life. The bitterness comes from the sense that we know for sure that we can never really regain them, they're gone forever."

The irreversibility of time means that there is no way to go back in time so it helps us to deal with the conflict of the bitter longing for what can never be again, together with the sweetness of having experienced it and being able to revisit it and relive it again.

Change, whether it's good or bad, is stressful. That's mostly because we're not 100 percent sure how much of it is within our control.

So when things begin to change, either very substantially, such as major events in a person's life, getting married or getting divorced, getting a new career, going back to school or graduating from school, it's comforting to have a nostalgic feeling for the past that reminds us that although we don't know what the future is going to bring, what we do know is that we know who we have been and who we are.

These pictures bring us back to the times when we were accepted and loved unconditionally.

"That is such a powerfully comforting phenomenon, knowing that there was a time in life when we didn't have to earn our love, or we didn't deserve it because we earned a certain amount of money or we were successful in a certain venue," Batcho said.

"Our parents, for example, or our siblings, or our friends simply loved us unconditionally. That is a wonderfully comforting feeling when we're undergoing any kind of turmoil in our personal lives."

So if you want to indulge in it a little more, check out these 50 Nostalgia-Instilling Posts For Kids Of The ’80s, ’90s And ’00s.