Can I control the unique organ I get?

With the new Metamorph league I'm getting a ton of hearts to take back to Tane's lab. Is this just based on RNG or is there a way I can force a particular unique organ to drop after filling the Metamorph's rating on maps?

If you have multiple Unique organs, and you want a specific Unique organ to drop, you should aim for a combination of body parts that will still result in a juiced up metamorph, but only have one Unique part slotted in the desired drop part slot.

Example: Say you have the following:

• a Unique Brain
• a Unique Liver
• a Unique Eyes

You are looking for a Unique Liver drop from the metamorph. Therefore you should aim for a combination that not only results in the maximum juice bar, but also looks something like:

• Common/Magic/Rare Brain
• Common/Magic/Rare Eyes
• Common/Magic/Rare Lungs
• Common/Magic/Rare Heart
• Unique Liver

This will ensure that you always get a Unique Liver upon defeating the metamorph.

If you set up your metamorph as the following:

• Unique Brain
• Common/Magic/Rare Eyes
• Common/Magic/Rare Lungs
• Common/Magic/Rare Heart
• Unique Liver

As of patch 3.9.1, every map boss has an equal unweighted chance to drop any of the 5 parts, so every boss can drop brains, eye, livers, lungs, and hearts.

This was a useful infographic I found while researching before Senpai provided their great answer. I'll just add it for completeness: