“Relationships are complicated,” a mother tells her son in a new trailer for Melissa Miller Costanzo’s “All These Small Moments.” Carla (Molly Ringwald, “Riverdale”) knows this to be true. When teenager Howie (Brendan Meyer, “The OA”) and his little brother (Sam McCarthy, “Condor”) ask her where their dad is, she doesn’t know the answer — or whether their marriage is over.

A coming-of-age drama, “All These Small Moments” follows Howie as he tries to make sense of his increasingly complicated home life. As a distraction from the chaos going on within his family, he becomes obsessed with Odessa (Jemima Kirke, “Girls”), a 30-year-old he sees on the bus. Odessa is also going through a hard time: she’s in the midst of a divorce.

“All These Small Moments” marks Costanzo’s feature directorial debut.

“I wrote this script because I had many personal feelings I wanted to explore that stemmed from different facets of my life: reflecting on the pain of first loves, grappling with forbidden ones, and dealing with love’s fickle nature,” the writer-director told us. “I hope people will reflect on their own ‘small moments’ that they continue to carry around with them, and on how our collective life and consciousness are formed by them,” she added.

When we asked her advice for other women filmmakers, Constanzo said, “Be vocal. If you’ve written something and you want to direct — say it. I remember the first time I sat down with my agents about this project and they asked if I wanted to direct and I said yes, and that was that.” She continued, “Producers were told, ‘If you want this project, she’s the director.’ Fortunately, it was never questioned, and it’s a real testament to my producers for believing in my vision.”

Costanzo previously directed the short film “The Busker,” and has worked in the art department of films such as “Precious,” “The Fighter,” and “If Beale Street Could Talk.”

“All These Small Moments” hits theaters January 17, followed by a digital release the next day.