The challenge for all of us, as the church, is how we can help these passionate Christians stay on track through their 20s, Stone writes.
We're the smartphone, social media generation.
We were raised to share our opinions, to speak our minds. By the age of 21, millions of us had significant education debt.
We were taught we could be anything, anyone, we wanted to be.
But that's a lot of pressure. We don't really know what we want. So we try things out. We take our time to commit. We wait to start our careers, to get married, to have a family.
We're told we're frittering away our 20s and that we need to settle down. But that's easier said than done in a world with high youth unemployment and even higher house prices.
So we live in the now. But in the back of our minds, we're worried that we're missing out on something. We wonder whether we should be doing more with our lives.
We go to church and our friends think it's odd, but "nice for us." And it seems like the church thinks we're a bit odd too. It tells us, in a slightly worried tone, that we are its future - we're not too sure what that means for today.
I'm a millennial Christian. A member of Generation Y.
We are one of the biggest challenges facing the church. We're also one of its greatest resources. We have unique gifts, traits and experiences to offer God's people and the world.
But we're in a minority among our peers and, in most cases, in the church. We need you to understand us, we need you to encourage us and, most of all, we need your prayers.
So who are we? We're the people who were born between 1980 and 2000, or thereabouts. The ones who were growing up over the millennium.
Stereotypes and generalizations can never accurately describe a group of people (let alone an entire generation) - but failing to make long-term commitments, having short attention spans and seeking happiness in the moment are also all regularly listed as examples of what is wrong with us.
Generation Y is underrepresented in the church; there are so few of us that we've actually been described as the lost generation. And we are, in turn, underrepresented on the mission field.
It's easy to put that down to the negative stereotypes. But there are many other legitimate reasons why young Christians are held back from full-time ministry abroad.
A few decades ago, giving up your life to go and serve in mission would have earned you a great deal of respect. That is not the case among millennials.
Becoming a missionary has always been countercultural, but choosing to step out and give at least four years to work overseas as a millennial is, quite frankly, an alien concept to most people in their 20s.
It's not only the decision to embark on overseas mission that is countercultural in this scenario - choosing to make a long-term commitment to one place, one organization, one job, is a rare thing to see in a generation where everything moves so quickly.
And this is not just having an impact on mission. Business is feeling the effects too. New entrants to the job market are unlikely to stick in any one place for long.
On top of lacking the security of property, many millennials are debt-ridden. The Generation Ys who have gone to university generally find themselves with significant debt by their early 20s.
Those who haven't been to university might be more financially secure, but they often don't yet have the skills or experience needed for the mission roles we're looking to fill these days.
Because it's not just people who have changed with our changing world - mission has changed too. Mission in this postmodern era looks different from 50, 30 or even 10 years ago.
Mission agencies like BMS World Mission are often looking to send capacity builders - people with specific skill sets who can train and equip local people to do the work long term.
Yet, mission agencies and the church shouldn't give up on my comfort-seeking, commitment-phobic, cash-poor generation.
We may be different from those who have come before us, but that could be a good thing.
Millennials don't want to be defined by lacking commitment, money and independence. There are plenty of positive generalizations true of Generation Y too.
We've grown up working in teams and we've been neighbors and friends with people from all over the world since childhood. That means we're collaborative and very willing to learn from the world church.
We've been raised to believe in serving the poor practically, so integral mission - sharing the gospel while meeting people's physical needs - is a concept that's quite natural to us.
We care about other people, and statistics show that loads of us are involved in volunteering locally.
Even the fact that we're less focused on the long-term has a positive side, as it means we're not so concerned with security, houses and pensions, and we're willing to step out and embrace the now.
Millennials aren't just stereotypes. We're not all sitting at home playing video games, living with our parents and floating from one job to the next without any drive or ambition.
Every year, BMS sees millennials come back from their time overseas on fire for God and passionate about mission and discipleship.
The challenge for all of us, as the church, is how we can help these passionate Christians stay on track through their 20s. How we can walk alongside them and help them use all of the wonderful gifts God has given them.
So, please pray for us. Pray for the Generation Ys who are asking, searching and wondering whether there is more to life.
And, if you can, get to know some of us. Encourage us. Share your wisdom with us.
Because while we might be the church of tomorrow, we're also part of the church today.
Sarah Stone is a writer for BMS World Mission. A longer version of this article first appeared in Winter 2016/2017 edition of Engage Magazine - a publication of BMS World Mission. It is used with permission. You can follow Stone on Twitter @Sarah_Stone and BMS @BMSWorldMission.