[Q] WiFi client and Access Point less than 5cm/2 inches appart

Hi

Quick hypothetical question.

What if anything happens if a wifi client and access point are sitting right next to each other and almost touching.
Is there any impact on 2.4GHz/5GHz access??
I googled a bit on half-dupex Ethernet as it's CSMA/CD which is close to CSMA/CA used in WiFi, but couldn't find anything.
Are there any timing/wave form issues when two antennas (client/access point) are almost touching???
Does the antenna mW power at such close range impact on each other???

Thank...

[Q] WiFi client and Access Point less than 5cm/2 inches appart