On the 25th and 26th of March we welcomed 35 high school and primary school teachers from all over the country in TIME workshop on lesson study and didactical design at V. gymnasium in Zagreb. On the first day lesson study was introduced. A study lesson was prepared by one of the teams. After the mathematical analysis, the lesson was performed live with a 3rd year class. The students’ task was to find a linear model for the data given and to analyse the mathematical background. The participants experienced lesson observation and reflection meeting. On the second day some guidelines for task design were introduced and the teams shared their experiences from the TIME project.