The long-missed New England summer is at its peak. Here in Connecticut, trees are green and flower buds are erupting into colour. It is beautiful. For postdocs, however, the season's arrival is a reminder of something not so uplifting. It is the time of year when we realize that many friendships that we have forged during our tenure are going to suffer as colleagues and friends graduate, move on to other endeavours and leave for faraway places.

A postdoctoral fellowship is, after all, a 'stepping stone' to independence as a scientist, a temporary stint meant to prepare one for a permanent position as the head of an academic lab. But this sterile definition does not take into account the people that one gets to know during this time, the people with whom one shares meals, ideas, feelings and good times. At the end of this academic year, many of my colleagues will leave in search of better work opportunities; I will inevitably follow their lead in the near future. This exodus may happen in any field as people leave to explore a new professional or academic venture, but it is common to postdocs in particular because their fellowships are typically brief — usually one to three years in duration — and their new jobs often take them to locations quite distant from those in which they completed their fellowships.

But although it is true that much of a postdoc's life is made up of short-lived encounters, those encounters are nonetheless deeply satisfying — in no small part because of the variety of people they involve. Among the friends I've made, for example, are a physicist who started his career as an air force cadet and then became a carpenter; a physician and a cell biologist who show reassuring constancy; and a graphic designer looking for her next adventure. All of these people will be etched on my heart and mind long after our paths have diverged. My experience at Yale University has been enhanced by their presence, their ideas and their words, and although our time together is evanescent, it has been priceless.

The moment has come for me to face this reality and say goodbye to some good friends. But even as the summer heralds some difficult farewells, I think of our wonderful times together and smile.