[{"course":"Math","students":[{studentID:"id_1",studentName:"Name 1"},{studentID:"id_2",studentName:"Name 2"}]},{"course":"English","students":[{studentID:"id_1",studentName:"Name 1"},{studentID:"id_3",studentName:"Name 3"}]},{"course":"Programming","students":[{studentID:"id_4",studentName:"Name 4"},{studentID:"id_5",studentName:"Name 5"}]},]

db.collection.aggregate([{$unwind:"$students"},{$match:{"students.studentID":"id_1"}}])