What is inside the mind of teenagers on Instagram?

Instagram is one of the most used social media with 45 million active users on each month. In Indonesia, the highest number of internet users is between the age of 13 34 years old. It shows that most of the new internet users are young people. In this research, we create a topic model for the Instagram caption of teenager users in Surabaya, Indonesia, using latent dirichlet allocation (LDA) method. By using pen and paper questionnaire, we collected total number of Instagram 494 valid accounts with 4,664 captions. The data were collected from January 2014 to June 2017. The process of modelling using LDA was performed by experimenting with a set of number of topics: 2, 3, 4 and 5. The two topics were selected because it has a small value of perplexity, which indicates that the model has a good level of conformity. The two topics represents two categories: school and relationship . It was found that the topic model was dominated by the relationship category.