Learn Spanish (Spain): Vamos a cambiar la papilla según crezca. - We are going to change the baby food as he grows.

We use the subjunctive after según when referring to a future action that hasn't happened yet. Because the baby's growth is an anticipated future event, we need the subjunctive crezca. If we were describing a repeated, habitual action in the present, like 'We always change the baby food as he grows,' we would use the indicative crece.

Could I use conforme instead of según in this sentence?

Yes! You could say conforme crezca or even a medida que crezca. All three expressions are used to talk about evolving situations and mean 'as he grows.' They all require the subjunctive here because the growth is in the future.

Why isn't there a subject pronoun like él or el bebé before crezca?

In Spanish, subject pronouns are often dropped when the context makes it obvious. Since papilla is baby food, it is naturally understood that a baby is doing the growing. If you wanted to be extra clear, you could place the subject after the verb: según crezca el bebé.

Is papilla just the word for 'baby food' in general?

It refers specifically to puréed, mashed, or mushy food, which is what babies typically eat. If you wanted to say 'baby food' in a broader sense, you might also hear comida para bebés, but papilla is the standard word for those little jars of purée or homemade mash.