Disclosed is a method of operating a laboratory instrument (100, 1000), wherein the laboratory instrument is configured for receiving a sample rack (112) with one or more sample tubes (126), wherein the laboratory instrument comprises a robotic head (106) for bringing a pipettor (108) into fluidic contact with the one or more sample tubes when the sample rack is in an operating position (122), wherein the robotic head is configured for loading the sample rack into the operating position, and wherein the method comprises the steps of: receiving (200) the sample rack by the laboratory instrument; and loading (202) the rack into the operating position using the robotic head.