Organic Crystals and Advanced Materials Guide
If your science is stalling because oil products are piling up, or you need a reliable path into yellow and purple science, Organic Crystals are one of the key materials to sort out. Start by getting the Plastic-based route working, then scale it cleanly, then switch to off-world mining once that option opens up. The goal is not just to make Organic Crystals once; it is to keep the whole oil chain steady enough that research keeps moving.
Start with the Plastic-based route, not the manual one
Organic Crystals can be made by hand from Plant Fuel and Log, but that route depends on manual collection, so treat it as a stopgap only. If you want steady progression, get Plastic production running first and use that to feed Organic Crystal automation as soon as you can.
Plastic is the standard automated input here, and it comes from Crude Oil through oil processing. That matters because Plastic is already one of the important early products from oil, and its role does not stop at Organic Crystals. You will also need it later for Particle Broadband, and that makes Plastic a long-term factory material rather than a temporary intermediate.
Organic Crystals then feed Titanium Crystals, which are mainly used for research. In other words, if you want to keep your Structure Matrix progression and later science tiers on track, 
Lay out enough Chemical Plants and oil support to keep the line moving
The Plastic-based Organic Crystal chain is best treated as a real production line, not a side project. Plastic input. That means you should think in paired capacity: if you expand Plastic, be ready to expand Organic Crystals with it.
The Chemical Plant recipe also consumes 5 
Plastic is used for Organic Crystals, 
Particle Broadband, and Explosive Unit production, so it is worth keeping a steady supply available. Organic Crystals are your main bottleneck material for research support, while Titanium Crystals are the direct reason you are making Organic Crystals in the first place.
Build the line with enough spacing that you can expand it without tearing down the whole setup. If you try to squeeze it into a cramped area, you will usually end up starving Plastic on one side and backing up Refined Oil on the other.
Solve the oil bottleneck before Organic Crystals choke your science
If the line feels unstable, look at oil throughput and hydrogen handling before you add more Chemical Plants. Scaling the end product without stabilizing the supporting refinery chain usually just creates more shortages downstream.
Plastic is a major sink for Crude Oil, and that is actually part of why it is so useful. It also remains relevant later for Particle Broadband, so the demand does not disappear after yellow science. That means you should avoid thinking of Plastic as “only for early progression.” It is one of the materials that keeps getting pulled into new chains.
So your priority order should be simple: keep Crude Oil processing stable, make sure Plastic output is steady, and only then add more Organic Crystal capacity. If your refinery is already stretched, more Chemical Plants will not fix it.
Use Organic Crystals as a stepping stone to Titanium Crystals and research
Organic Crystals have a single direct use: crafting Titanium Crystals. That makes them a bottleneck material, not an end goal. Build only as much as your Titanium Crystal plan and research demand actually require, then expand when science starts asking for more.
This is especially important because Organic Crystals are part of the transition into Structure Matrix production through the early material chain. Plastic supports that transition in two ways: first through Organic Crystals and Titanium Crystals, and later through Particle Broadband for Information Matrix production. So even if you are only thinking about yellow science right now, you are really laying the foundation for purple science too.
Do not overproduce Organic Crystals just because the recipe exists. Feed the amount your current science needs, keep your oil chain balanced, and expand only when research consumption starts to outpace your buffer.
Switch to off-world mining once interstellar travel opens up
After interstellar travel is unlocked, the easiest large-scale source of Organic Crystals is direct mining from resource veins on exotic planets outside the starting star system. Once you can do that, you should strongly consider shifting bulk supply away from the oil chain.
That switch matters because before version 0.7.18.6914, 
Crude Oil could be harvested indefinitely, but that is no longer the case. In the current progression, you should not assume oil can solve everything forever. Use it while it is convenient, but do not build your entire Organic Crystal future around it if off-world logistics are available.
You can also find Organic Crystals in some plants, with purple plants giving higher concentrations. That is useful in a pinch, but it is still not the answer for scaling. Treat plant harvesting as supplemental, not as a foundation for a growing science factory.
Keep Plastic production alive for purple science and other late-game uses
Even after Organic Crystals stop being your main concern, do not dismantle Plastic production. Plastic is required for Particle Broadband, which is part of Information Matrix production, and there are no alternate recipes that replace Plastic in that role. Once purple science begins, Plastic becomes a permanent requirement.
Plastic is also used in Explosive Unit production, so it keeps showing up in places that matter beyond the science screen. Since Chemical Plant Plastic production is relatively slow compared with some other oil recipes, you should plan both factory count and power draw with later demand in mind.
The safest approach is to keep Plastic alive as a core oil product, then let off-world Organic Crystal mining reduce the pressure on your refinery chain. That way you can reserve your oil processing for the things that still need it, instead of rebuilding the same supply line every time science advances.