If you want to track a person’s activities for a day, you could call them up every ten minutes and ask what they’re doing. Easier, though, would be to provide them with a journal to log their own actions. Scientists often rely on a method akin to the first to track how cells change over time; they pick cells out of a group at set time points and take a snapshot of their genetic activity.
Click here for original story, Scientists engineer dna ‘receipt book’ to store cells’ history
Source: Phys.org