The 1993 film Jurassic Park was the world's highest-grossing film at the time of its release, making over $914 million USD (US dollars) in revenue. The premise of the film is that scientists were able to revive dinosaurs by getting their DNA out of the gut of ancient mosquitoes preserved in amber. The fragments of dinosaur DNA are amplified using PCR (polymerase chain reaction), the gaps are filled in with frog DNA, and the repaired genome is then injected into an ostrich egg and brought to term in an artificial womb. Since the movie was released, curious people have asked, "Could that actually be possible?"
Often, when a biologist is asked about the feasibility of Jurassic Park, they get intellectually stuck on one of the numerous scientific inaccuracies in the dinosaur revival scheme, using that as a justification to dismiss the possibility, even in principle or after centuries of scientific progress. Despite these inaccuracies, there is a substantial chance that dinosaur revival could indeed be possible, though it would necessarily involve advanced biotechnology -- a biotechnology several decades more advanced than today's, at least. However, biotechnological advances between 1993 and today have already caused some of the earlier doubters of Jurassic Park to think twice before condemning the possibility.
There are numerous instances of fictional glossing-over in the biotechnological scenario presented in Jurassic Park. Let's separate truth from fiction. First off, isolating ancient DNA from long-dead organisms trapped in amber is entirely possible. However, there is great disagreement as to whether it is possible to recover authentic DNA from specimens more than about a million years old. In the early 1990s, it was reported that ancient DNA had been recovered from stingless bees, termites, weevils, one dinosaur, plants, and bacteria dating all the way back to 80 million year old specimens from the Cretaceous era. Unfortunately, a later critical review found that these claims were all very tenuous, and that aside from two highly controversial instances of 300 million year old bacterial DNA recovery from rock salt, it is unlikely that DNA much older than a million years has ever been successfully recovered and amplified. The dinosaur DNA turned out to be a human Y chromosome, introduced to the sample via contamination.
There is still great disagreement as to whether the recovery of truly ancient DNA is possible. Whether it is or not, it has been confirmed that more recent DNA, including DNA from Neanderthals and mammoths, has indeed been recovered. There are, however, further problems with the Jurassic Park scenario. Filling in gaps in dinosaur DNA with frog DNA is likely to be extremely difficult, if possible at all. One would need to know which frog genes are homologous with which dinosaur genes, which would likely require a huge amount of dinosaur DNA fragments and sequencing data. Input the wrong genes, and the animal might not even grow past the embryo stage.
The third major challenge with the Jurassic Park approach is getting a suitable egg for the artificial dinosaur gamete to be injected into. An ostrich egg would not work. Instead, an egg of the exact same species would be required. This could theoretically be synthesized from the original genetic material, but it would be difficult. This challenge is not addressed in Jurassic Park -- instead it is glossed over.
If the three main challenges listed (recovery of DNA, repairing the genome, synthetic egg of the same species) can be overcome, then a Jurassic Park scenario could become possible in real life. Until then, science will go on as always. In any case, it's far more likely that recently extinct species, such as mammoths and Neanderthals, will be revived before any dinosaurs.