I came across this interesting article on SBS which shares of the scientific theory behind this experience. Known as contextual-binding theory.
It is well established that learning in the brain happens by a process of association. If A and B occur together, they become associated. Contextual-binding theory goes a step further: A and B are associated not just with one other, but also with the context in which they occurred.
What is context? It’s not just your physical location – it’s a mental state that also comprises the thoughts, emotions, and other mental activity you’re experiencing at a given moment.Adam Osth Senior Lecturer, University of Melbourne
Looking at photos of past family members triggers moments of past family experience. The article goes on to share that our brain is like a google search engine. The clearer you are in what you are searching for the better results will be retrieved, same with your memory.
Every time I travel back to Melbourne this mass of emotions, feelings and memories come flooding back. Whilst I have fond memories of Melbourne, actually being there amplifies my experience and deepens the feelings.