(Context: I have a PhD in genomics - but not necessarily an expert in this sub-field) It is possible, but still difficult, to edit cells in-place. One example

(Context: I have a PhD in genomics - but not necessarily an expert in this sub-field) It is possible, but still difficult, to edit cells in-place. One example is the liver, a highly vascularized tissue (lots of blood vessels). This means that you can use a blood-based delivery method, e.g. blood infusion of CRISPR components + other compounds that allow these components to enter cells. Over time, more of the liver cells are edited and you can reach a reasonable proportion of the cells using this method using current techniques (40-90%). Note that for many diseases you would not have to reach 100% of the cells in order to have a positive effect on health. There are a few labs working on better targeted delivery methods. In general the approach is to "wrap" CRISPR components in an envelope that is able to target specific cell-surface proteins for the cell type of interest.