Tissue Sorting ?

[Nmr]

Hi guys
A very good morning to all of you. during last week i was staying in peace suddenly one of my friend came to me and told me that '' i have misunderstanding with this title (the tissue sorting ) and i want to help me'' he thought that i know something about it .

So, now i want from you guys to help me to understand this topic (tissue sorting) and if anyone has an articles or something ales please post their link here to read them before i meet my friend again.

Note: the only thing that i have known about thins topic till now as below;

A process in which two tissues invade or envelope one another is of key importance in complex tissue.
Concept
•Imagine 2 liquids (oil and water)
•The interfacial energy at the surface correspond to the surface tension, γo/w (dynes/cm)
•In order to inject air at the interface, work must be performed on the system to achieve a total interfacial energy of γo/A + γw/A

and now i am confused about that and really i want to understand this topic with 3 days and write something about.

I appreciate any effort of you to help me.

Thankful