# Updating UnstructredGrid after Adding Cell
**URL:** https://discourse.vtk.org/t/updating-unstructredgrid-after-adding-cell/2345
**Category:** Development
**Created:** [December 27, 2019, 10:15am UTC](https://discourse.vtk.org/t/updating-unstructredgrid-after-adding-cell/2345 "2019-12-27T10:15:41Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ChristopherWaters](https://discourse.vtk.org/u/ChristopherWaters)
#### Post date: [December 27, 2019, 10:15am UTC](https://discourse.vtk.org/t/updating-unstructredgrid-after-adding-cell/2345/1 "2019-12-27T10:15:41Z")
**Current System (bottom-up):**
- **points** (vtkSmartPointer\< vtkPoints \>)
- **topology** (vtkSmartPointer\< vtkCellArray \>)
- **unGrid** (vtkSmartPointer\< vtkUnstructuredGrid \>)
- **mapper** (vtkSmartPointer\< vtkDataSetMapper \>)
- **actor** (vtkSmartPointer\< vtkActor \>)
**My Attempt to Add New Cell and Update:**
I have added a new cell to **topology** and am confused on how to update this system. It consists of existing points, so have tried:
```auto
topology->InsertNextCell(newCell);
unGrid->GetCells()->Modified();
```
**Questions:**
- What thing(s) do I need to update(call Modifed() ) on, just **unGrid**?
- Since I need to specify the cell types when I SetCells() for **unGrid** , do I need to do this again when I add a new cell(since it could be of a new type)?
**Notes:**
- vtk 8.2.0
- Must use unstructured grid
---
### Author:  [@ChristopherWaters](https://discourse.vtk.org/u/ChristopherWaters)
#### Post date: [December 29, 2019, 9:02am UTC](https://discourse.vtk.org/t/updating-unstructredgrid-after-adding-cell/2345/2 "2019-12-29T09:02:33Z")
I thought this would be a pretty fundamental question, so I’ll just come back with updates if I make any more progress.
---
### Author:  [@ChristopherWaters](https://discourse.vtk.org/u/ChristopherWaters)
#### Post date: [December 29, 2019, 9:43am UTC](https://discourse.vtk.org/t/updating-unstructredgrid-after-adding-cell/2345/3 "2019-12-29T09:43:53Z")
Very simple solution, after trying many things I simply **replaced:**
```auto
unGrid->GetCells()->Modified();
```
**With:**
`unGrid->Modified();`