Choosing a 12 well plate without buying the wrong case
At twelve wells, the plate is bought for what happens inside the well. Surface, inserts, and well access decide the purchase; the well count is the easy part.
Most wrong 12 well purchases are surface mistakes (the cells never attached, or attached when they should not have) and insert mistakes (the membrane or pore size the assay never wanted). This guide walks the decisions in the order they bite.
Start from the job
Name what the well has to do. Grow adherent cells to harvest: a treated flat bottom plate. Run a two-compartment system: an insert plate, and the insert catalog becomes the real decision. Image live cultures: a treated plate with a flat, clear bottom, or a glass bottom plate for high magnification. Process samples in parallel: the polypropylene deep well version. Writing the job down first eliminates most of the catalog in one pass.
Surface treatment: the adherent versus suspension choice
Tissue culture treated (TC treated) plates have their polystyrene growth surface plasma treated so it wets properly and carries a charge that cells can attach to; adherent cells spread and grow on it. Non-treated plates keep the natural hydrophobic polystyrene surface, so cells cannot attach and grow in suspension instead. The rule is short: adherent cells need a treated plate, suspension cells need a non-treated one, and trying to grow adherent cells on an untreated plate is the most common reason a 12 well culture never takes off. Coated plates, collagen or poly-lysine over the treated surface, are the step beyond for weakly adherent and primary cells, and the coating most primary cultures are actually specified on.
Inserts: the second plate inside the plate
A 12 well insert hangs a membrane basket in the well, dividing it into an upper and a lower compartment that share medium but not cells. The decisions are membrane material (PET and polycarbonate are the common pair), pore size (small pores for transport and co-culture where cells must stay put, large pores for migration and invasion where cells must pass), and whether the membrane needs to be clear for imaging. Buy the plate and inserts as a system: hanging geometry varies, and an insert that sits at the wrong height changes the medium depths the assay was calibrated on.
Material, sterility, and lids
Culture plates are polystyrene, clear and treatable, sterile with lids. Deep well versions are polypropylene for solvent and temperature range. Glass bottom 12 well plates swap the well floor for a thin borosilicate sheet at cover glass thickness, about 0.17 mm, for confocal and high numerical aperture work, at glass prices and glass fragility; for routine imaging a standard flat bottom is enough. Sterility is not optional for culture and not worth paying for on processing plates that will be washed or used for chemistry.
The fit checks
A 12 well culture plate is shallow and takes a standard lid; nearly everything in the lab accepts it. The checks that fail are accessory checks: whether your microscope stage insert takes the footprint (it does, it is standard), whether insert plates clear the incubator shelf above, and whether a deep well version fits the shaker clamp and the handler's plate definitions. Confirm the deep well height before the case arrives, not at the bench.
Related guides
Common questions
What insert pore size do I need?
It follows the assay. Transport and co-culture studies use small pores (0.4 um class) that pass molecules and medium but hold cells in their compartment. Migration and invasion assays use large pores (8 um class) that cells can actively move through. The middle sizes serve specialized barriers. If the protocol names a pore size, treat it as a specification, not a suggestion.
Are there glass bottom 12 well plates?
Yes. A glass bottom plate replaces the plastic well floor with a thin borosilicate glass sheet, about 0.17 mm, in a polystyrene frame, for high resolution and confocal microscopy. Growth area matches the standard plate at 3.8 cm2. For plate reader work and low magnification imaging, a standard flat bottom plate is enough.
When is 12 wells the wrong choice?
When the experiment is a screen (that is 48, 96, or 384), when you need maximum cells per condition in few wells (that is 6), or when the readout is a plate reader assay that gains nothing from big wells. Format follows the limiting resource: conditions, material per well, or access to the well.