During vertebrate development, clustered Hox genes are activated in a precise time-sequence, leading to expression patterns necessary to properly establish the body plan. The mechanism underlying this in cis timing phenomenon (The Hox clock) has remained elusive ever since its initial observation in 1989, due to the difficulty to approach it using the small and complex early gastrulating mouse embryos. I will introduce this topic and discuss an alternative possibility, which is to use pseudo-embryos produced out of ES cells (referred to as gastruloids) to address this (largely overdue) question and will show some preliminary data indicating that this system may allow us to more efficiently tackle this issue in the next few years to come.