The talk will present the ELT wavefront control activities related to phasing and shaping of the primary segmented mirror. The ELT primary mirror is composed of 798 quasi-hexagonal segments, which are controlled in piston, tip, tilt, and shape with nanometric accuracy. The ELT Phasing and Diagnostic Station (PDS) located at the Nasmyth station will provide all sensing functions needed to establish and maintain the telescope alignment under demanding environmental conditions. This presentation will introduce the control equipment involved in the control and calibration schemes, the different calibration methods, and highlight the relevant experience at GTC that led to the technical baseline.